A117674 - OEIS

A117674

Prime numbers whose sum of digits is a triangular number.

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

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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