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A263457 Integers n such that A006218(n) is triangular. 0
1, 2, 5, 15, 20, 26, 55, 68, 92, 108, 150, 156, 336, 346, 364, 423, 563, 586, 682, 798, 866, 951, 1194, 1734, 1888, 2790, 3102, 3150, 3506, 4210, 4611, 5820, 6766, 6943, 7665, 7701, 7888, 8734, 8772, 9410, 10114, 10839, 10969, 11014, 11453, 11630, 11947, 12357 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

Table of n, a(n) for n=1..48.

EXAMPLE

If A027750 is displayed as a regular triangle:

   1;      <--1

   1,  2;       <--2

   1,  3;  1,

   2,  4;  1,  5;       <--5

   1,  2,  3,  6;  1,

   7;  1,  2,  4,  8;  1,

   3,  9;  1,  2,  5, 10;  1,

  11;  1,  2,  3,  4,  6, 12;  1,

  13;  1,  2,  7, 14;  1,  3,  5, 15;      <-- 15

PROG

(PARI) lista(nn) = {s = 0; for (n=1, nn, s += numdiv(n); if (ispolygonal(s, 3), print1(n, ", ")); ); }

CROSSREFS

Cf. A000005, A006218, A027750, A175345.

Sequence in context: A032841 A058221 A146122 * A146121 A066883 A146120

Adjacent sequences:  A263454 A263455 A263456 * A263458 A263459 A263460

KEYWORD

nonn

AUTHOR

Michel Marcus, Oct 19 2015

STATUS

approved

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Last modified August 4 12:45 EDT 2020. Contains 336201 sequences. (Running on oeis4.)