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.

Showing 1-3 of 3 results.

A114518 Numbers n such that A008475(n) is prime.

Original entry on oeis.org

2, 3, 5, 6, 7, 10, 11, 12, 13, 17, 18, 19, 22, 23, 24, 28, 29, 31, 34, 36, 37, 40, 41, 43, 47, 48, 52, 53, 54, 58, 59, 61, 67, 71, 72, 73, 76, 79, 82, 83, 88, 89, 97, 100, 101, 103, 107, 108, 109, 112, 113, 118, 127, 131, 137, 139, 142, 148, 149, 151, 157, 160, 162, 163
Offset: 1

Views

Author

Leroy Quet, Dec 05 2005

Keywords

Examples

			24 = 2^3 * 3 and 2^3 + 3 = 11, which is prime. So 24 is included.

Links

Crossrefs

Cf. A008475, A114519, A114520, A114522.

Programs

  • Mathematica
    f[n_] := Plus @@ Power @@@ FactorInteger[n]; Select[Range[165], PrimeQ[f[ # ]] &] (* Ray Chandler, Dec 07 2005 *)
  • PARI
    A008475(n)=local(t);if(n<1,0,t=factor(n);sum(k=1,matsize(t)[1],t[k,1]^t[k,2])); for(i=1,500,if(isprime(A008475(i)),print1(i,","))) (Herrgesell)

Extensions

Extended by Ray Chandler and Lambert Herrgesell (zero815(AT)googlemail.com), Dec 07 2005

A114521 a(n) = A008475(A114520(n)).

Original entry on oeis.org

5, 7, 7, 11, 13, 11, 11, 19, 13, 13, 19, 17, 29, 31, 17, 23, 43, 19, 29, 31, 23, 61, 73, 41, 37, 83, 19, 47, 31, 67, 53, 103, 29, 17, 109, 37, 127, 71, 23, 139, 41, 151, 83, 31, 43, 181, 193, 131, 23, 101, 23, 199, 29, 41, 107, 19, 61, 43, 37, 113, 71, 229, 23, 67, 241
Offset: 1

Views

Author

Leroy Quet, Dec 05 2005

Keywords

Examples

			24 (which is composite) is the sixth term of sequence A114520. 24 = 2^3 * 3 and 2^3 + 3 = 11 (which is prime). So a(6) = 11.

Crossrefs

Cf. A008475, A114518, A114519, A114520, A047820.

Programs

  • Mathematica
    f[n_] := Plus @@ Power @@@ FactorInteger[n]; f /@ Select[Select[Range[500], PrimeQ[f[ # ]] &], ! PrimeQ[ # ] &] (* Ray Chandler, Dec 07 2005 *)
  • PARI
    A008475(n)=local(t);if(n<1,0,t=factor(n);sum(k=1,matsize(t)[1],t[k,1]^t[k,2])); for(i=1,900,if(!isprime(i)&&isprime(A008475(i)),print1(A008475(i),","))) (Herrgesell)

Extensions

Extended by Ray Chandler and Lambert Herrgesell (zero815(AT)googlemail.com), Dec 07 2005

A163409 Subsequence of composite terms of A008475.

Original entry on oeis.org

4, 8, 9, 9, 8, 16, 9, 10, 25, 15, 27, 10, 32, 14, 12, 21, 16, 12, 15, 14, 25, 49, 27, 20, 16, 15, 22, 12, 33, 16, 64, 18, 16, 21, 26, 14, 39, 28, 18, 18, 21, 81, 14, 22, 45, 32, 16, 20, 27, 34, 49, 24, 35, 51, 20, 22, 21, 15, 55, 18, 40, 24, 28, 33, 22, 24, 16, 121, 63, 44, 35, 125, 18, 128, 46, 20
Offset: 1

Views

Author

Leroy Quet, Jul 27 2009

Keywords

Crossrefs

A008475, A114519, A163408

Formula

a(n) = A008475(A163408(n)).

Extensions

More terms from Max Alekseyev, Oct 14 2012
Showing 1-3 of 3 results.

Started in 1964 by Neil J. A. Sloane | Maintained by The OEIS Foundation Inc.

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