A068343 a(n) is a prime power and sum of all prime powers <= a(n) is A025475.

1, 2111, 43997, 69499

Offset: 1

Author

Naohiro Nomoto, Mar 08 2002

Keywords

• nonn
• more

Comments

No other terms up to 10^9. - Michel Marcus, Mar 26 2020

a(5) > 10^12, if it exists. - Giovanni Resta, Apr 12 2020

Examples

			2111 is a term because 1+2+3+4+5+7+8+..+2111 = 323761 = 569^2.
		

Crossrefs

Cf. A000961, A024918, A025475.

Programs

PARI

ispp1(n) = isprimepower(n) || (n==1); \\ A000961
ispp2(n) = ispower(n, , &p) && isprime(p) || n==1; \\ A025475
lista(nn) = {my(s=0); for (n=1, nn, if (ispp1(n), s += n; if (ispp2(s), print1(n, ", "));););} \\ Michel Marcus, Mar 26 2020