A179532 a(n) = 2^ceiling(n*(n+1)/3).

1, 2, 4, 16, 128, 1024, 16384, 524288, 16777216, 1073741824, 137438953472, 17592186044416, 4503599627370496, 2305843009213693952, 1180591620717411303424, 1208925819614629174706176, 2475880078570760549798248448

Offset: 0

Author

Paul Barry, Jan 08 2011

Keywords

• nonn

Comments

Hankel transform of A128750. Satisfies (4,0) Somos-4 recurrence 4*a(n-1)*a(n-3)/a(n-4) = a(n),n>3.

Links

• G. C. Greubel, Table of n, a(n) for n = 0..99

Programs

Magma

[2^Ceiling((n(n+1))/3): n in [0..20]]; // G. C. Greubel, Aug 14 2018

Mathematica

Table[2^Ceiling[(n(n+1))/3],{n,0,20}] (* Harvey P. Dale, Sep 25 2013 *)

PARI

vector(20,n,n--; 2^ceil(n*(n+1)/3)) \\ G. C. Greubel, Aug 14 2018

Formula

2^A007980.

a(n) = a(-1-n) for all n in Z. - Michael Somos, Aug 14 2018