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 A117674 Prime numbers whose sum of digits is a triangular number. 2
 3, 19, 37, 73, 109, 127, 163, 181, 271, 307, 433, 523, 541, 613, 631, 811, 1009, 1063, 1117, 1153, 1171, 1423, 1531, 1621, 1801, 1999, 2017, 2053, 2143, 2161, 2251, 2341, 2503, 2521, 3061, 3313, 3331, 3511, 3889, 4051, 4231, 4789, 4969, 4987, 5023, 5113 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 LINKS Amiram Eldar, Table of n, a(n) for n = 1..10000 EXAMPLE 1999 is in the sequence because it is a prime number and the sum of its digits 1+9+9+9 = 28 is a triangular number. MATHEMATICA t={}; Do[m = Total[IntegerDigits[Prime[n]]]; If[IntegerQ[(Sqrt[8*m + 1]-1)/2], AppendTo[t, Prime[n]]], {n, 700}]; t (* Jayanta Basu, Apr 27 2013 *) PROG (PARI) isok(p) = isprime(p) && ispolygonal(sumdigits(p), 3); \\ Michel Marcus, Feb 08 2021 CROSSREFS Intersection of A000040 and A187744. Cf. A000217, A007953. Sequence in context: A187828 A088786 A147237 * A114704 A167053 A131542 Adjacent sequences: A117671 A117672 A117673 * A117675 A117676 A117677 KEYWORD nonn,base AUTHOR Luc Stevens (lms022(AT)yahoo.com), Apr 27 2006 STATUS approved

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Last modified March 20 18:36 EDT 2023. Contains 361391 sequences. (Running on oeis4.)