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A068343 a(n) is a prime power and sum of all prime powers <= a(n) is A025475. 0
1, 2111, 43997, 69499 (list; graph; refs; listen; history; text; internal format)
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

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Last modified October 15 21:38 EDT 2021. Contains 348034 sequences. (Running on oeis4.)