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A053723 Number of 5-core partitions of n. 10
1, 1, 2, 3, 5, 2, 6, 5, 7, 5, 12, 6, 12, 6, 10, 11, 16, 7, 20, 15, 12, 12, 22, 10, 25, 12, 20, 18, 30, 10, 32, 21, 24, 16, 30, 21, 36, 20, 24, 25, 42, 12, 42, 36, 35, 22, 46, 22, 43, 25, 32, 36, 52, 20, 60, 30, 40, 30, 60, 30, 62, 32, 42, 43, 60, 24, 66, 48, 44, 30, 72, 35, 72 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,3

COMMENTS

Number 11 of the 74 eta-quotients listed in Table I of Martin 1996.

REFERENCES

B. C. Berndt, H. H. Chan, S.-S. Huang, S.-Y. Kang, J. Sohn and S. H. Son, The Rogers-Ramanujan continued fraction, J. Comput. Appl. Math. 105 (1999), 9-24.

Garvan, F., Kim, D. and Stanton, D., Cranks and t-cores, Inventiones Math. 101 (1990), 1-17.

Freeman J. Dyson, Missed opportunities, Bull. Amer. Math. Soc. 78 (1972), 635-652. see pages 636-637.

Y. Martin, Multiplicative eta-quotients, Trans. Amer. Math. Soc. 348 (1996), no. 12, 4825-4856, see page 4852 Table I.

S. Ramanujan, The Lost Notebook and Other Unpublished Papers, Narosa Publishing House, New Delhi, 1988; see p. 54 (1.52).

LINKS

T. D. Noe, Table of n, a(n) for n=0..1000

B. C. Berndt, The Rogers-Ramanujan continued fraction.

F. Garvan, D. Kim and D. Stanton, Cranks and t-cores.

FORMULA

Given g.f. A(x), then B(x) = x * A(x) satisfies 0 = f(B(x), B(x^2), B(x^4)) where f(u, v, w) = v^3 + 2 * u*v*w + 4 * u*w^2 - u^2*w. - Michael Somos, May 02 2005

G.f.: (1/x) * (Sum_{k>0} kronecker(k, 5) * x^k / (1 - x^k)^2). - Michael Somos, Sep 02 2005

G.f.: Product_{k>0} (1 - x^(5*k))^5 / (1 - x^k) = 1/x * (Sum_{k>0} k * x^k * (1 - x^k) * (1 - x^(2*k)) / (1 - x^(5*k))). - Michael Somos, Jun 17 2005

G.f.: (1/x) * Sum_{a, b, c, d, e in Z^5} x^((a^2 + b^2 + c^2 + d^2 + e^2) / 10) where a + b + c + d + e = 0, (a, b, c, d, e) == (0, 1, 2, 3, 4) (mod 5). - [Dyson 1972] Michael Somos, Aug 08 2007

Euler transform of period 5 sequence [ 1, 1, 1, 1, -4, ...].

Expansion of q^(-1) * eta(q^5)^5 / eta(q) in powers of q.

a(n) = b(n + 1) where b(n) is multiplicative with b(5^e) = 5^e, b(p^e) = (p^(e+1) - 1) / (p - 1) if p == 1, 4 (mod 5), b(p^e) = (p^(e+1) + (-1)^e) / (p + 1) if p == 2, 3 (mod 5).

Convolution inverse of A109063. a(n) = (-1)^n * A138512(n+1).

Convolution of A227216 and A229802. - Michael Somos, Jun 10 2014

EXAMPLE

G.f. = 1 + x + 2*x^2 + 3*x^3 + 5*x^4 + 2*x^5 + 6*x^6 + 5*x^7 + 7*x^8 + ...

G.f. = q + q^2 + 2*q^3 + 3*q^4 + 5*q^5 + 2*q^6 + 6*q^7 + 5*q^8 + 7*q^9 + ...

MATHEMATICA

a[n_]:=Total[KroneckerSymbol[#, 5]*n/# & /@ Divisors[n]]; Table[a[n], {n, 1, 73}] (* Jean-Fran├žois Alcover, Jul 26 2011, after PARI prog. *)

a[ n_] := SeriesCoefficient[ QPochhammer[ q^5]^5 / QPochhammer[ q], {q, 0, n}]; (* Michael Somos, Jul 13 2012 *)

a[ n_] := With[{m = n + 1}, If[ m < 1, 0, DivisorSum[ m, m/# KroneckerSymbol[ 5, #] &]]]; (* Michael Somos, Jul 13 2012 *)

PROG

(PARI) {a(n) = local(A); if( n<0, 0, A = x * O(x^n); polcoeff( eta(x^5 + A)^5 / eta(x + A), n))};

(PARI) {a(n) = if( n<0, 0, n++; sumdiv( n, d, kronecker( d, 5) * n/d))};

(PARI) {a(n) = if( n<0, 0, n++; direuler( p=2, n, 1 / (1 - p*X) / (1 - kronecker( p, 5) * X))[n])};

CROSSREFS

Cf. A053724, A109063, A138512. column t=5 of A175595.

Cf. A227216, A229802.

Sequence in context: A239692 A126833 * A138512 A201652 A066949 A073481

Adjacent sequences:  A053720 A053721 A053722 * A053724 A053725 A053726

KEYWORD

easy,nonn,mult

AUTHOR

James A. Sellers, Feb 11 2000

STATUS

approved

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Last modified December 21 07:50 EST 2014. Contains 252297 sequences.