cp's OEIS Frontend

This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.

A134180 Indices of primes in A007468.

Original entry on oeis.org

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

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Author

Enoch Haga, Oct 16 2007

Keywords

Comments

Compute sums of k distinct sequential primes (no overlap). If the sums are prime add their indices to the sequence.

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.
		

Crossrefs

Cf. A007468. Corresponding primes are listed in A134179.

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