|
|
A007241
|
|
McKay-Thompson series of class 2A for the Monster group with a(0) = 24.
(Formerly M5176)
|
|
197
|
|
|
1, 24, 4372, 96256, 1240002, 10698752, 74428120, 431529984, 2206741887, 10117578752, 42616961892, 166564106240, 611800208702, 2125795885056, 7040425608760, 22327393665024, 68134255043715, 200740384538624
(list;
graph;
refs;
listen;
history;
text;
internal format)
|
|
|
OFFSET
|
-1,2
|
|
REFERENCES
|
J. M. Borwein and P. B. Borwein, Pi and the AGM, Wiley, 1987, p. 195.
S. Ramanujan, Modular Equations and Approximations to pi, pp. 23-39 of Collected Papers of Srinivasa Ramanujan, Ed. G. H. Hardy et al., AMS Chelsea 2000. See page 26.
N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
|
|
LINKS
|
|
|
FORMULA
|
G.f. 48 + 64(g_n^(24) + g_n^(-24)) where q = e^(-Pi sqrt(n)) and g_n is Ramanujan's class invariant. - Michael Somos, Apr 20 2005
|
|
EXAMPLE
|
G.f. = 1/q + 24 + 4372*q + 96256*q^2 + 1240002*q^3 + 10698752*q^4 + ...
|
|
MATHEMATICA
|
a[n0_] := Module[{n=n0, A}, If[n < -1, 0, n++; A = Product[ 1 - x^(2*k-1) , {k, 1, Quotient[n+1, 2]}]^24; SeriesCoefficient[ A + x*48 + x^2*4096/A, {x, 0, n}]]]; Table[ a[n], {n, -1, 16}] (* Jean-François Alcover, Oct 16 2012, after Michael Somos *)
a[ n_] := SeriesCoefficient[ With[{A = q QPochhammer[ -q, q]^24}, -80 + (1 + 64 A)^2 / A], {q, 0, n}]; (* Michael Somos, Apr 06 2015 *)
nmax = 50; CoefficientList[Series[48*x + 4096*x^2*Product[(1 + x^k)^24, {k, 1, nmax}] + Product[1/(1 + x^k)^24, {k, 1, nmax}], {x, 0, nmax}], x] (* Vaclav Kotesovec, Apr 01 2017 *)
|
|
PROG
|
(PARI) {a(n) = my(A); if( n<-1, 0, n++; A = prod( k=1, (n+1)\2, 1 - x^(2*k - 1), 1 + x * O(x^n))^24; polcoeff( A + x*48 + x^2 * 4096/A, n))}; /* Michael Somos, Feb 07 2003 */
(PARI) {a(n) = my(A); if( n<-1, 0, n++; A = x * O(x^n); A = (eta(x^2 + A) / eta(x + A))^24; polcoeff( -80*x + (1 + 64 * x * A)^2 / A, n))}; /* Michael Somos, Apr 06 2015 */
|
|
CROSSREFS
|
|
|
KEYWORD
|
nonn,nice
|
|
AUTHOR
|
|
|
STATUS
|
approved
|
|
|
|