OFFSET
0,1
REFERENCES
B. Runge, On Siegel modular forms I, J. Reine Angew. Math., 436 (1993), 57-85.
LINKS
G. C. Greubel, Table of n, a(n) for n = 0..45
B. Runge, Codes and Siegel modular forms, Discrete Math. 148 (1996), 175-204.
FORMULA
a(n) = 2^(n^2 + 2*n + 2) * Product_{j=1..n} (2^j - 1).
a(n) = (-1)^n * 2^(n^2 + 2*n + 2) * (2, 2)_{n}, where (q, q)_{n} is the q-Pochhammer symbol. - G. C. Greubel, Aug 04 2022
MAPLE
seq(2^(n^2+2*n+2)*mul(2^i-1, i=1..n), n=0..10);
MATHEMATICA
a[n_]:= (-1)^n*2^(n^2 +2*n+2)*QPochhammer[2, 2, n];
Table[a[n], {n, 0, 15}] (* G. C. Greubel, Aug 04 2022 *)
PROG
(Magma)
A027639:= func< n | n eq 0 select 4 else 2^(n^2+2*n+2)*(&*[2^j-1: j in [1..n]]) >;
[A027639(n): n in [0..15]]; // G. C. Greubel, Aug 04 2022
(SageMath)
from sage.combinat.q_analogues import q_pochhammer
def A027639(n): return (-1)^n*2^(n^2 + 2*n + 2)*q_pochhammer(n, 2, 2)
[A027639(n) for n in (0..15)] # G. C. Greubel, Aug 04 2022
(PARI) a(n) = my(ret=1); for(i=1, n, ret = ret<<i-ret); ret << (n^2 + 2*n + 2); \\ Kevin Ryde, Aug 13 2022
CROSSREFS
KEYWORD
nonn,nice,easy
AUTHOR
STATUS
approved