OFFSET
0,1
LINKS
Seiichi Manyama, Table of n, a(n) for n = 0..1000
Michael Somos, Introduction to Ramanujan theta functions
Eric Weisstein's World of Mathematics, Ramanujan Theta Functions
FORMULA
Euler transform of period 12 sequence [ -1, 0, 0, 0, 0, 0, 0, 0, 0, 0, -1, -1, ...].
G.f.: Product_{k>0} (1 - x^(12*k)) * (1 - x^(12*k - 1)) * (1 - x^(12*k - 11)).
Convolution inverse of A210964.
EXAMPLE
G.f. = 1 - x - x^11 + x^14 + x^34 - x^39 - x^69 + x^76 + x^116 - x^125 + ...
G.f. = q^25 - q^49 - q^289 + q^361 + q^841 - q^961 - q^1681 + q^1849 + ...
PROG
(PARI) {a(n) = my(m = 24*n + 25); if( issquare(m, &m) && (m%12==5 || m%12==7), (-1)^((m+6) \ 12))};
CROSSREFS
KEYWORD
sign
AUTHOR
Michael Somos, Jan 10 2015
STATUS
approved