OFFSET
1,2
LINKS
Seiichi Manyama, Table of n, a(n) for n = 1..200
L. Sallows, M. Gardner, R. K. Guy and D. E. Knuth, Serial isogons of 90 degrees, Math. Mag. 64 (1991), 315-324.
FORMULA
product[ {1+x^(2i+1)},i=0,1,...,4n-1] = 1+...+2*a(n)*x^(8n^2)+.... (g.f.). - R. J. Mathar, May 08 2007
a(n) = A292476(2*n)/2. - Seiichi Manyama, Sep 18 2017
MAPLE
A107350 := proc(n) res := 1 ; for i from 0 to 4*n-1 do res := taylor(res*(1+x^(2*i+1)), x=0, 8*n^2+1) ; od ; coeftayl(res, x=0, 8*n^2)/2 ; end: for n from 1 to 25 do printf("%d, ", A107350(n)) ; od ; # R. J. Mathar, May 08 2007
MATHEMATICA
a[n_] := SeriesCoefficient[Product[x^(2k - 1) + 1/x^(2k - 1), {k, 1, 4n}], {x, 0, 0}]/2;
Table[a[n], {n, 1, 25}] (* Jean-François Alcover, Mar 10 2023 *)
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
N. J. A. Sloane, May 23 2005
EXTENSIONS
More terms from R. J. Mathar, May 08 2007
STATUS
approved