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A119952
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Number of partitions of n into parts relatively prime to 63 and not == 2 (mod 4).
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1
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1, 1, 1, 2, 3, 4, 5, 6, 9, 11, 13, 17, 22, 27, 32, 40, 51, 61, 72, 88, 108, 128, 150, 180, 217, 255, 297, 351, 416, 485, 562, 657, 770, 891, 1026, 1190, 1380, 1587, 1818, 2092, 2409, 2754, 3139, 3590, 4105, 4670, 5299, 6026, 6854, 7761, 8770, 9926, 11231
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OFFSET
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0,4
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COMMENTS
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Ramanujan theta functions: f(q) (see A121373), phi(q) (A000122), psi(q) (A010054), chi(q) (A000700).
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REFERENCES
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B. C. Berndt, Ramanujan's Notebooks Part III, Springer-Verlag, see p. 426 Entry 19(ii).
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LINKS
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Table of n, a(n) for n=0..52.
M. Somos, Introduction to Ramanujan theta functions
Eric Weisstein's World of Mathematics, Ramanujan Theta Functions
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FORMULA
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Expansion of psi(-x^7) * psi(-x^9) / (psi(-x) * psi(-x^63)) in powers of x where psi() is a Ramanujan theta function.
Expansion of q^6 * eta(q^2) * eta(q^7) * eta(q^9) * eta(q^28) * eta(q^36) * eta(q^126) / (eta(q) * eta(q^4) * eta(q^14) * eta(q^18) * eta(q^63) * eta(q^252)) in powers of q.
Euler transform of period 252 sequence A209198.
G.f. is a period 1 Fourier series which satisfies f(-1 / (252 t)) = f(t) where q = exp(2 pi i t).
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EXAMPLE
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1 + x + x^2 + 2*x^3 + 3*x^4 + 4*x^5 + 5*x^6 + 6*x^7 + 9*x^8 + 11*x^9 + ...
q^-6 + q^-5 + q^-4 + 2*q^-3 + 3*q^-2 + 4*q^-1 + 5 + 6*q + 9*q^2 + 11*q^3 + ...
a(7) = 6 since 5 + 1 + 1 = 4 + 3 = 4 + 1 + 1 + 1 = 3 + 3 + 1 = 3 + 1 + 1 + 1 + 1 = 1 + 1 + 1 + 1 + 1 + 1 + 1 in 6 ways.
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PROG
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(PARI) {a(n) = local(A); if( n<0, 0, A = x * O(x^n); polcoeff( eta(x^2 + A) * eta(x^7 + A) * eta(x^9 + A) * eta(x^28 + A) * eta(x^36 + A) * eta(x^126 + A) / (eta(x + A) * eta(x^4 + A) * eta(x^14 + A) * eta(x^18 + A) * eta(x^63 + A) * eta(x^252 + A)), n))}
(PARI) {a(n) = local(A); if( n<0, 0, A = sum( k=0, (sqrtint(8*n + 1) - 1)\2, (-x)^((k^2 + k)/2), x * O(x^n)); polcoeff( subst(A + x * O(x^(n\7)), x, x^7) * subst(A + x * O(x^(n\7)), x, x^9) / A / subst(A + x * O(x^(n\63)), x, x^63), n))}
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CROSSREFS
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Cf. A209198.
Sequence in context: A080112 A123924 A036023 * A102571 A064278 A220570
Adjacent sequences: A119949 A119950 A119951 * A119953 A119954 A119955
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KEYWORD
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nonn
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AUTHOR
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Michael Somos, May 30 2006
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STATUS
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approved
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