A261148 - OEIS

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A261148

Prime-Indexed Primes (PIPs) k such that the sum of all PIPs <= k is a prime.

3, 11, 31, 59, 83, 211, 331, 773, 1297, 1433, 1471, 1621, 2027, 2477, 3637, 4153, 4787, 4877, 5623, 7699, 9103, 9619, 11743, 12097, 12959, 13037, 13591, 13709, 14177, 14969, 15299, 16411, 16703, 16921, 19463, 19577, 21379, 22093, 22721, 24107, 24151, 24419, 24509, 24671, 28657

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OFFSET

1,1

COMMENTS

This is a strict subset of A006450: {k from A006450 | Sum_{j=1..k} A006450(j) is prime}.

It seems from observation that asymptotically a(n)/A006450(n) ~ 7.5*log(n) - e. But might this just be coincidence? I certainly have no proof. - Michael Turniansky, Aug 21 2015

LINKS

Michael Turniansky, Table of n, a(n) for n = 1..508

EXAMPLE

11 is in the sequence because A006450(1) + A006450(2) + A006450(3) = 3 + 5 + 11 = 19, a prime number.

MATHEMATICA

L={}; s=0; p=2; While[Length@L < 100, If[PrimeQ[s+=(q = Prime@p)], AppendTo[L, q]]; p = NextPrime@ p]; L (* Giovanni Resta, Aug 21 2015 *)

PROG

(APL (NARS200 dialect)) (0π+\A←¯2π¯2π⍳1000)/A

(PARI) lista(nn) = {s = 0; forprime(p=2, nn, q = prime(p); s += q; if (isprime(s), print1(q, ", ")); ); } \\ Michel Marcus, Aug 20 2015

CROSSREFS

Cf. A006450.

Sequence in context: A057172 A277167 A277049 * A071568 A097081 A093406

Adjacent sequences: A261145 A261146 A261147 * A261149 A261150 A261151

KEYWORD

nonn,easy

AUTHOR

Michael Turniansky, Aug 10 2015

STATUS

approved