A066561 - OEIS

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A066561

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

1, 6, 3, 28, 10, 6, 21, 120, 36, 10, 55, 36, 78, 28, 15, 496, 136, 36, 171, 120, 21, 66, 253, 120, 300, 78, 351, 28, 406, 120, 465, 2016, 66, 136, 105, 36, 666, 190, 78, 120, 820, 210, 903, 528, 45, 276, 1081, 528, 1176, 300, 153, 780, 1378, 378, 55, 1176, 171

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OFFSET

1,2

COMMENTS

See A344005 for an efficient algorithm. - N. J. A. Sloane, Jul 13 2021

LINKS

T. D. Noe, Table of n, a(n) for n = 1..1000

FORMULA

a(n) = A000217(A011772(n)). - Bill McEachen, Dec 28 2021

PROG

(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

CROSSREFS

Cf. A000217, A011772, A344005, A345988.

Sequence in context: A285607 A287546 A285559 * A073872 A281677 A282303

Adjacent sequences: A066558 A066559 A066560 * A066562 A066563 A066564

KEYWORD

nonn

AUTHOR

Amarnath Murthy, Dec 17 2001

EXTENSIONS

More terms from Naohiro Nomoto, Dec 26 2001

STATUS

approved