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

1, 2111, 43997, 69499

Offset

1,2

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

Links

Table of n, a(n) for n=1..4.

Example

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

Prog

(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

Crossrefs

Cf. A000961, A024918, A025475.

Sequence in context: A284962 A146895 A300008 * A256518 A046334 A046382

Adjacent sequences: A068340 A068341 A068342 * A068344 A068345 A068346

Keyword

nonn,more

Author

Naohiro Nomoto, Mar 08 2002

Status

approved