A134180 Indices of primes in A007468.
1, 3, 5, 7, 9, 13, 23, 25, 29, 55, 117, 119, 123, 173, 187, 193, 205, 213, 223, 249, 255, 259, 265, 285, 299, 311, 329, 351, 393, 397, 411, 483, 487, 513, 515, 525, 563, 587, 597, 607, 637, 645, 647, 679, 709, 789, 871, 877, 911, 953, 971, 985, 1015, 1051, 1075
Offset: 1
Examples
a(2)=3 because this k value is the index for the next 3 primes in sequence to be summed. k=1 is 2, k=2 is 3+5 and k=3 is 7+11+13=31. The sums at k=1 and k=3 are prime, while k=2 is composite.
Links
- Chai Wah Wu, Table of n, a(n) for n = 1..1000
Programs
-
UBASIC
10 K=1 20 A=nxtprm(A): B=B+A: C=C+1: if C<>K then 20: else 30 30 L=B/K 31 print K;B;: Q=prmdiv(B): if Q=B then print B; "-": stop: else 40 40 B=0: K=K+1: C=0: goto 20
Comments