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A066561 a(n) is the smallest triangular number divisible by n. 6

%I #21 Dec 29 2021 02:17:19

%S 1,6,3,28,10,6,21,120,36,10,55,36,78,28,15,496,136,36,171,120,21,66,

%T 253,120,300,78,351,28,406,120,465,2016,66,136,105,36,666,190,78,120,

%U 820,210,903,528,45,276,1081,528,1176,300,153,780,1378,378,55,1176,171

%N a(n) is the smallest triangular number divisible by n.

%C See A344005 for an efficient algorithm. - _N. J. A. Sloane_, Jul 13 2021

%H T. D. Noe, <a href="/A066561/b066561.txt">Table of n, a(n) for n = 1..1000</a>

%F a(n) = A000217(A011772(n)). - _Bill McEachen_, Dec 28 2021

%o (PARI) { for (n=1, 1000, s=0; b=0; while (b==0, s++; t=s*(s+1)/2; if (t%n == 0, b=1)); write("b066561.txt", n, " ", t) ) } \\ _Harry J. Smith_, Mar 05 2010

%Y Cf. A000217, A011772, A344005, A345988.

%K nonn

%O 1,2

%A _Amarnath Murthy_, Dec 17 2001

%E More terms from _Naohiro Nomoto_, Dec 26 2001

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Last modified April 23 07:16 EDT 2024. Contains 371905 sequences. (Running on oeis4.)