OFFSET
1,2
COMMENTS
All terms are square and triangular; a subsequence of A001110.
REFERENCES
C. Alsina and R. B. Nelson, Charming Proofs: A Journey into Elegant Mathematics, MAA, 2010. See p. 4.
FORMULA
a(n) = (1/8)*sinh(2^(n-2)*arccosh(17))^2. [Alexander R. Povolotsky, Aug 14 2011]
a(n+2) = 4*a(n+1)*(a(n+1)/(2*a(n))-1)^2, a(1)=1, a(2)=36. [Alexander R. Povolotsky, Aug 15 2011]
a(n) = A001110(2^(n-1)). - Ivan N. Ianakiev, Mar 11 2014
MAPLE
T:=n->n*(n+1)/2; t1:=[1]; for n from 1 to 7 do t1:= [op(t1), T(8*t1[nops(t1)])]; od: t1;
MATHEMATICA
NestList[(8#(8#+1))/2&, 1, 7] (* Harvey P. Dale, Jan 20 2015 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
N. J. A. Sloane, Feb 18 2011
STATUS
approved