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 A083676 Triangular numbers whose sum of aliquot divisors is a prime number. 1
 21, 55, 171, 325, 595, 741, 1081, 1711, 2485, 3081, 3655, 7021, 11325, 13861, 14365, 15931, 23005, 23653, 23871, 29403, 31375, 32131, 44551, 45451, 48205, 52003, 53301, 60031, 65341, 65703, 67161, 74691, 81003, 87571, 92665, 108811, 110215, 114481, 115921 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 LINKS Donovan Johnson, Table of n, a(n) for n = 1..1000 Shyam Sunder Gupta, Fascinating Triangular Numbers. EXAMPLE a(2) = 55 because sum of aliquot divisors of 55 = 1+5+11 = 17, which is a prime number. PROG (PARI) c=0; for(m=1, 34021, t=m*(m+1)\2; if(isprime(sigma(t)-t), c++; write("b083676.txt", c " " t))) /* Donovan Johnson, May 20 2013 */ CROSSREFS Sequence in context: A144302 A180674 A067431 * A264104 A236694 A292368 Adjacent sequences:  A083673 A083674 A083675 * A083677 A083678 A083679 KEYWORD nonn AUTHOR Shyam Sunder Gupta, Jun 15 2003 STATUS approved

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Last modified July 24 14:51 EDT 2021. Contains 346273 sequences. (Running on oeis4.)