cp's OEIS Frontend

This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.

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A294475 a(n) = (-1)^n * A294359(n) / (n+1)^2.

Original entry on oeis.org

1, 1, 4, 34, 480, 9806, 265810, 9031672, 369946976, 17763808796, 979237588724, 60980447270606, 4235264029208444, 324666123698241278, 27234289478093347800, 2481803404797989770784, 244176750407604670797512, 25799371668963384500485336, 2913817630601365750195653270, 350339454794537924316740555298, 44680403720910899340653296364594
Offset: 0

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Author

Paul D. Hanna, Nov 03 2017

Keywords

Comments

It is conjectured that all terms are even after the initial '1,1'.
Sequence A294359(n) = [x^n] F(x)^(-(n+1)^2) such that F(x) = Sum_{n>=0} x^A003714(n) where A003714 is the Fibbinary numbers.
Fibbinary numbers are integers whose binary representation contains no consecutive ones (see A003714 for definition).

Examples

			Given the characteristic function of the Fibbinary numbers (A003714):
F(x) = 1 + x + x^2 + x^4 + x^5 + x^8 + x^9 + x^10 + x^16 + x^17 + x^18 + x^20 + x^21 + x^32 + x^33 + x^34 + x^36 + x^37 + x^40 + x^41 + x^42 + x^64 + x^65 + x^66 + x^68 + x^69 + x^72 + x^73 + x^74 + x^80 +...+ x^A003714(n) +...
such that F(x) = F(x^2) + x*F(x^4),
then this sequence equals the coefficients of x^n in F(x)^(-(n+1)^2).
ILLUSTRATION OF TERMS.
The table of coefficients of x^k in F(x)^(-n^2) begins:
n=1: [1, -1, 0, 1, -2, 1, 2, -4, 2, 3, -8, 7, 4, -16, 16, 2, -30, ...];
n=2: [1, -4, 6, 0, -19, 40, -26, -56, 166, -160, -110, 560, -705, ...];
n=3: [1, -9, 36, -75, 36, 279, -942, 1278, 531, -5956, 11700, ...];
n=4: [1, -16, 120, -544, 1548, -2192, -2720, 23936, -63426, 67984, ...];
n=5: [1, -25, 300, -2275, 12000, -45005, 112450, -116350, -441375, ...];
n=6: [1, -36, 630, -7104, 57573, -353016, 1668774, -5996664, ...];
n=7: [1, -49, 1176, -18375, 209426, -1846859, 13024690, -74680760, ...];
n=8: [1, -64, 2016, -41600, 631216, -7491392, 72180992, -578027008, ...]; ...
in which the main diagonal, divided by (-1)^n*(n+1)^2, forms this sequence:
A = [1, 4/2^2, 36/3^2, 544/4^2, 12000/5^2, 353016/6^2, 13024690/7^2, ...].
RELATED SERIES.
Define g.f. A(x) = Sum_{n>=0} a(n)*x^n, then
A(x) = 1 + x + 4*x^2 + 34*x^3 + 480*x^4 + 9806*x^5 + 265810*x^6 + 9031672*x^7 + 369946976*x^8 + 17763808796*x^9 + 979237588724*x^10 +...
and the logarithm of A(x) begins:
Log(A(x)) = x + 7*x^2/2 + 91*x^3/3 + 1767*x^4/4 + 46181*x^5/5 + 1525351*x^6/6 + 61073419*x^7/7 + 2878197983*x^8/8 + 156203074099*x^9/9 + 9599753499547*x^10/10 +  659252738855129*x^11/11 + 50047297413657447*x^12/12 +...
in which it appears that the coefficients consist entirely of odd integers.
		

Crossrefs

Formula

a(n) = (-1)^n * [x^n] F(x)^(-(n+1)^2) / (n+1)^2 such that F(x) = F(x^2) + x*F(x^4), where F(x) = Sum_{n>=0} x^A003714(n) and A003714 is the Fibbinary numbers.
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