A205006 - OEIS

A205006

a(n) = s(k)-s(j), where (s(k),s(j)) is the least pair of distinct triangular numbers for which n divides their difference.

2, 2, 3, 4, 5, 12, 7, 8, 9, 20, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 56, 29, 30, 31, 32, 33, 34, 35, 72, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 132, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 156, 79, 80, 81

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OFFSET

1,1

COMMENTS

For a guide to related sequences, see A204892.

LINKS

Antti Karttunen, Table of n, a(n) for n = 1..23515

MATHEMATICA

(See the program at A205002.)

PROG

(PARI) A205006(n) = for(k=2, oo, my(sk=binomial(k+1, 2)); for(j=1, k-1, if(!((sk-binomial(j+1, 2))%n), return(sk-binomial(j+1, 2))))); \\ Antti Karttunen, Sep 27 2018

CROSSREFS

Cf. A000217, A205002, A205007, A204892.

Cf. A318894 (gives the positions where a(n) is not n).

Sequence in context: A014535 A210642 A263140 * A123560 A060407 A083702

Adjacent sequences: A205003 A205004 A205005 * A205007 A205008 A205009

KEYWORD

nonn

AUTHOR

Clark Kimberling, Jan 21 2012

EXTENSIONS

More terms from Antti Karttunen, Sep 27 2018

STATUS

approved