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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
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 (list; graph; refs; listen; history; text; internal format)
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

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Last modified February 5 23:07 EST 2023. Contains 360091 sequences. (Running on oeis4.)