A307950 Primes that are the sum of two prime-indexed triangular numbers.

31, 43, 97, 157, 181, 193, 281, 367, 463, 499, 587, 709, 769, 1051, 1381, 1459, 1621, 1831, 1861, 2081, 2281, 2293, 2377, 2473, 2647, 2707, 2713, 2729, 2767, 2837, 3019, 3163, 3251, 3259, 3313, 3709, 3863, 4021, 4447, 4591, 4759, 4943, 4951, 5051, 5179, 5647, 5791, 5861, 5869, 5881, 6217, 6271

Offset: 1

Author

J. M. Bergot and Robert Israel, May 07 2019

Keywords

• nonn

Comments

Primes of the form A034953(i) + A034953(j).

There are primes with more than one expression of this form; e.g., 18749 = A034953(4) + A034953(44) = A034953(19) + A034953(42).

Examples

			a(3) = 97 is a term because 97 = 6 + 91 is prime where 6=A000217(3) and 91=A000217(13) are in A034953.
		

Links

• Robert Israel, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A000217, A034953, A117112.

Programs

Maple

A034953:= map(t ->t*(t+1)/2, [seq(ithprime(i),i=1..100)]):
A:= select(t -> t <= A034953[-1]+3 and isprime(t), {seq(seq(A034953[i]+A034953[j],j=i+1..100),i=1..99)}):
sort(convert(A,list));