

A215797


Numbers n such that n(n+1)/2 + 1 is a power of 2.


3




OFFSET

1,3


COMMENTS

No other terms < 10^6.  T. D. Noe, Aug 25 2012
This sequence maps to the RamanujanNagell squares (8*(n*(n+1)/2)+1) and is therefore complete.  Raphie Frank, Aug 26 2012
All terms in this sequence follow form floor[2^((2*x  1)/2)]; x = {0, 1, 2, 3, 7}.  Raphie Frank, Mar 03 2013


LINKS



FORMULA



MATHEMATICA

Select[Range[0, 1000], IntegerQ[Log[2, 1 + #(#+1)/2]]&] (* T. D. Noe, Aug 25 2012 *)


PROG

(PARI) for(n=0, 100, if(ispolygonal(2^n1, 3), print1(sqrtint(2*2^n2)", "))) \\ Charles R Greathouse IV, Mar 04 2013


CROSSREFS

Cf. A060728, A038198 (two references to the RamanujanNagell problem).


KEYWORD

nonn,fini,full


AUTHOR



STATUS

approved



