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

Offset: 1

Author

Luc Stevens (lms022(AT)yahoo.com), Apr 27 2006

Keywords

• nonn
• base

Examples

			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.
		

Links

• Amiram Eldar, Table of n, a(n) for n = 1..10000

Crossrefs

Intersection of A000040 and A187744.

Cf. A000217, A007953.

Programs

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 *)

PARI

isok(p) = isprime(p) && ispolygonal(sumdigits(p), 3); \\ Michel Marcus, Feb 08 2021