A077207 Triangular number index of A077206(n).

1, 5, 32, 126, 141, 447, 4001, 4472, 40001, 44721, 141421, 447214, 3162278, 4472136, 34641016, 109544512, 400000001, 447213596, 3464101616, 10954451150, 31622776602, 77459666925, 316227766017, 774596669241, 1414213562373

Offset

1,2

Links

Table of n, a(n) for n=1..25.

Prog

(PARI) {rT(m) = ceil((sqrt(8*m+1)-1)/2)} {T(n) = (n*(n+1))/2} m=1; for(n=2, 50, k=rT((m%10)*10^(n-1)); while(T(k)%10==0, k++); m=T(k); print1(" ", k)) (Alekseyev)

Crossrefs

Cf. A077206.

Sequence in context: A184536 A363411 A089574 * A319790 A273623 A359522

Adjacent sequences: A077204 A077205 A077206 * A077208 A077209 A077210

Keyword

base,nonn

Author

Amarnath Murthy, Nov 02 2002

Extensions

Corrected and extended by Max Alekseyev, Feb 15 2005

Status

approved