A077003 a(n) = index of triangular number A077002(n).

1, 1, 1, 2, 4, 9, 22, 59, 167, 501, 1585, 5258, 18215, 65676, 245738, 951740, 3806961, 15696503, 66594623, 290279233, 1298168196, 5948954024, 27903067710, 133818411722, 655573653819, 3277868269096, 16713914267109, 86848046111951

Offset

1,4

Links

Table of n, a(n) for n=1..28.

Maple

a[1] := 1:b[1] := 1:for n from 2 to 100 do a[n] := floor(evalf(-1/2+1/2*sqrt(1+8*(n-1)*a[n-1])+1/10^50, 300)):b[n] := a[n]:a[n] := a[n]*(a[n]+1)/2:od:seq(b[l], l=1..100);

Crossrefs

Cf. A077002.

Sequence in context: A321994 A035053 A000571 * A210726 A046917 A237770

Adjacent sequences: A077000 A077001 A077002 * A077004 A077005 A077006

Keyword

nonn

Author

Amarnath Murthy, Oct 26 2002

Extensions

More terms from Sascha Kurz, Jan 26 2003

Status

approved