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A262716
a(n) = 31^(2*n+1).
2
31, 29791, 28629151, 27512614111, 26439622160671, 25408476896404831, 24417546297445042591, 23465261991844685929951, 22550116774162743178682911, 21670662219970396194714277471, 20825506393391550743120420649631, 20013311644049280264138724244295391
OFFSET
0,1
COMMENTS
31*a(n) is a square.
In general, Sum_{i>=0} 1/m^(2*i+1) = m/(m^2-1) when |m|>1. In this case, Sum_{i>=0} 1/a(i) = 31/960. [Bruno Berselli, Oct 07 2015]
FORMULA
G.f.: 31/(1 - 961*x).
a(n) = 961*a(n-1).
MATHEMATICA
31^Range[1, 30, 2]
PROG
(Magma) [31^(2*n+1): n in [0..15]];
(PARI) Vec(31/(1 - 961*x) + O(x^30)) \\ Michel Marcus, Oct 07 2015
(PARI) vector(15, n, n--; 31^(2*n+1)) \\ Bruno Berselli, Oct 07 2015
(Sage) [31^(2*n+1) for n in (0..15)] # Bruno Berselli, Oct 07 2015
CROSSREFS
Second bisection of A009975 (powers of 31).
Cf. similar sequences listed in A262715.
Sequence in context: A239167 A263585 A176349 * A033176 A263163 A188956
KEYWORD
nonn,easy
AUTHOR
Vincenzo Librandi, Oct 07 2015
STATUS
approved