

A104777


Integer squares congruent to 1 mod 6.


3



1, 25, 49, 121, 169, 289, 361, 529, 625, 841, 961, 1225, 1369, 1681, 1849, 2209, 2401, 2809, 3025, 3481, 3721, 4225, 4489, 5041, 5329, 5929, 6241, 6889, 7225, 7921, 8281, 9025, 9409, 10201, 10609, 11449, 11881, 12769, 13225, 14161, 14641, 15625, 16129
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OFFSET

1,2


COMMENTS

Exponents of powers of q in expansion of eta(q^24).
A033683(a(n)) = 1.


LINKS

Table of n, a(n) for n=1..43.
Index to sequences with linear recurrences with constant coefficients, signature (1,2,2,1,1)


FORMULA

G.f. ( 124*x22*x^224*x^3x^4 ) / ( (1+x)^2*(x1)^3 ).  R. J. Mathar, Feb 20 2011
a(n)=A007310(n)^2=1+24*A001318(n1).
a(n) = 9*n^2  9*n + 5/2 + (1)^n * (3*n  3/2). a(n+4) = 2*a(n+2)  a(n) + 72.  Robert Israel, Dec 12 2014


EXAMPLE

eta(q^24) = q  q^25  q^49 + q^121 + q^169  q^289  q^361 + ...


MAPLE

seq(9*(n1/2)^2 + 1/4 + (1)^n * (3*n  3/2), n = 1 .. 100); # Robert Israel, Dec 12 2014


PROG

(PARI) {a(n) = (3*n  1  n%2)^2};


CROSSREFS

Cf. A007310, A001318.
Sequence in context: A110013 A109861 A106564 * A131706 A110015 A110586
Adjacent sequences: A104774 A104775 A104776 * A104778 A104779 A104780


KEYWORD

nonn,changed


AUTHOR

Michael Somos, Mar 24 2005


STATUS

approved



