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%I #11 Apr 12 2020 03:52:47
%S 1,2111,43997,69499
%N a(n) is a prime power and sum of all prime powers <= a(n) is A025475.
%C No other terms up to 10^9. - _Michel Marcus_, Mar 26 2020
%C a(5) > 10^12, if it exists. - _Giovanni Resta_, Apr 12 2020
%e 2111 is a term because 1+2+3+4+5+7+8+..+2111 = 323761 = 569^2.
%o (PARI)
%o ispp1(n) = isprimepower(n) || (n==1); \\ A000961
%o ispp2(n) = ispower(n, , &p) && isprime(p) || n==1; \\ A025475
%o lista(nn) = {my(s=0); for (n=1, nn, if (ispp1(n), s += n; if (ispp2(s), print1(n, ", "));););} \\ _Michel Marcus_, Mar 26 2020
%Y Cf. A000961, A024918, A025475.
%K nonn,more
%O 1,2
%A _Naohiro Nomoto_, Mar 08 2002
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