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Bessel Moment Polynomial


The Bessel moment polynomials p_n(u) are the polynomials defined by the even-power sums

 p_n(x^2)=sum_(k=0)^inftyk^(2n)[J_k(2x)]^2
(1)

for positive integers n and real x, where J_k is a Bessel function of the first kind (Moya-Cessa 2026). Each has degree n and positive integer coefficients for the powers u through u^n, with no constant term. These are distinct from the Bessel polynomials.

Writing

 p_n(u)=sum_(m=1)^na_(n,m)u^m,
(2)

the coefficients are given by the finite sum

 a_(n,m)=1/((m!)^2)sum_(j=0)^(m-1)(-1)^j(2m; j)(m-j)^(2n)
(3)

for 1<=m<=n (Moya-Cessa 2026). The first few polynomials are

p_1(u)=u
(4)
p_2(u)=u+3u^2
(5)
p_3(u)=u+15u^2+10u^3
(6)
p_4(u)=u+63u^2+140u^3+35u^4
(7)
p_5(u)=u+255u^2+1470u^3+1050u^4+126u^5.
(8)

The linear coefficient is a_(n,1)=1, and the leading coefficient is half the central binomial coefficient, a_(n,n)=(2n; n)/2. The leading coefficients for n=1, 2, ... are 1, 3, 10, 35, 126, ... (OEIS A001700), with a_(n,n) corresponding to term n-1 in the OEIS indexing.

The recurrence relation

 p_(n+1)(u)=(ud/(du))^2p_n(u)+4up_n(u)-2int_0^up_n(t)dt
(9)

for n>=1, together with p_1(u)=u, generates the family (Moya-Cessa 2026).

The classical Bessel function of the first kind addition identity

 sum_(k=-infty)^infty[J_k(2x)]^2e^(iky)=J_0(4xsiny/2)
(10)

provides a generating function for the even-power sums. Differentiating at y=0 gives

 p_n(x^2)=((-1)^n)/2[(d^(2n))/(dy^(2n))J_0(4xsiny/2)]_(y=0),
(11)

where only powers of x through x^(2n) can contribute (Moya-Cessa 2026).


See also

Bessel Function of the First Kind, Bessel Polynomial

Portions of this entry contributed by Héctor M. Moya-Cessa

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References

Moya-Cessa, H. M. "Bessel Moment Polynomials." Appl. Math. Inf. Sci. 20, 1371-1375, 2026. https://doi.org/10.18576/amis/200519.NIST Digital Library of Mathematical Functions. "Sums." §10.23. https://dlmf.nist.gov/10.23.Sloane, N. J. A. Sequence A001700 in "The On-Line Encyclopedia of Integer Sequences."

Cite this as:

Weisstein, Eric W., with contributions by Héctor M. Moya-Cessa. "Bessel Moment Polynomial." From MathWorld--A Wolfram Resource. https://mathworld.wolfram.com/BesselMomentPolynomial.html

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