A256464 a(n) is the index, in the A256440 triangle, of the first row where n is the n-th term of the row.

1, 2, 5, 4, 13, 6, 23, 9, 19, 13, 43, 12, 59, 22, 27, 19, 79, 19, 97, 22, 41, 35, 113, 24, 89, 43, 59, 33, 157, 31, 173, 41, 77, 61, 101, 36, 211, 71, 95, 45, 239, 46, 257, 59, 71, 86, 281, 48, 209, 73, 127, 73, 331, 62, 167, 67, 143, 111, 373, 60, 389, 121

Offset

1,2

Comments

The integers for which a(n)=n are 1, 2, 4, 6, 12, 24, 36, 48, 60, ... : A004394.

The integers for which a(n)=n-1 are 3, 8, 18, 30, 72, ...: A247022 (except 3).

Links

Table of n, a(n) for n=1..62.

Example

Triangle A256440 starts:
1;
1, 2;
1, 3, 2;
1, 3, 2, 4;
1, 5, 3, 2, 4;
1, 5, 3, 2, 4, 6;
1, 7, 5, 3, 2, 4, 6;
...
a(1)=1 because row 1 is the first row where 1 is the 1st term of the row.
a(2)=2 because row 2 is the first row where 2 is the 2nd term of the row.
a(3)=5 because row 5 is the first row where 3 is the 3rd term of the row.

Prog

(PARI) posf(n) = {i = n; stop = 0; while (! stop, v = vector(i, k, sigma(k)/k); w = vecsort(v, , 1); pos = posv(n, w); if (pos == n, stop=1, i++); ); i; }

Crossrefs

Cf. A004394, A247022, A256440.

Sequence in context: A346595 A126356 A121274 * A111681 A073122 A277020

Adjacent sequences: A256461 A256462 A256463 * A256465 A256466 A256467

Keyword

nonn

Author

Michel Marcus, Mar 30 2015

Status

approved