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.

A134532 Numbers k such that the sum of the digits of 5^k is prime.

Original entry on oeis.org

1, 2, 4, 5, 6, 7, 13, 19, 20, 22, 26, 27, 29, 33, 34, 36, 41, 43, 44, 50, 54, 55, 58, 59, 60, 66, 69, 70, 74, 75, 81, 85, 91, 95, 97, 99, 100, 101, 110, 112, 125, 127, 129, 131, 133, 134, 136, 142, 143, 145, 146, 148, 153, 156, 157, 163, 165, 178, 187, 189, 190, 196
Offset: 1

Views

Author

Paolo P. Lava and Giorgio Balzarotti, Oct 30 2007

Keywords

Examples

			5^2=25 and 2+5=7 is prime.

Links

Crossrefs

Cf. A076203, A134533, A134534, A134535.

Programs

  • Maple
    P:=proc(k) if isprime(convert(convert(5^k,base,10),`+`)) then k; fi; end: seq(P(n),n=1..200);
  • Mathematica
    a={};For[n=1, n<200, n++, If[PrimeQ[Plus@@IntegerDigits[5^n]], AppendTo[a, n]]];a (* Vincenzo Librandi, Apr 17 2013 *)

Extensions

Corrected name and new Maple code by_Paolo P. Lava_, Jun 24 2024

A134533 Numbers n such that the sum of the digits of 7^n is prime.

Original entry on oeis.org

1, 2, 4, 8, 10, 12, 18, 19, 22, 24, 25, 32, 33, 35, 45, 56, 57, 58, 59, 60, 72, 73, 76, 81, 82, 84, 88, 100, 102, 103, 104, 105, 117, 118, 125, 136, 138, 142, 147, 149, 162, 188, 190, 192, 195, 201, 203, 206, 210, 212, 232, 240, 246, 252, 262, 264, 265, 269, 270, 280
Offset: 1

Views

Author

Paolo P. Lava and Giorgio Balzarotti, Oct 30 2007

Keywords

Examples

			7^2=49 and 4+9=13 is prime.

Links

Crossrefs

Cf. A076203, A134532, A134534, A134535.

Programs

  • Maple
    P:=proc(n) local cont,i,k,w; if isprime(n) then cont:=0; while cont<1000 do cont:=cont+1; w:=0; k:=n^cont; while k>0 do w:=w+k-(trunc(k/10)*10); k:=trunc(k/10); od; if isprime(w) then print(cont); fi; od; fi; end: P(7);
  • Mathematica
    a={}; For[n=1, n<700, n++, If[PrimeQ[Plus@@IntegerDigits[7^n]], AppendTo[a, n]]];a (* Vincenzo Librandi, Apr 17 2013 *)

A134535 Numbers n such that the sum of the digits of 13^n is prime.

Original entry on oeis.org

3, 6, 10, 14, 15, 24, 30, 33, 34, 39, 40, 47, 53, 57, 61, 71, 75, 76, 80, 81, 83, 88, 89, 92, 102, 103, 106, 117, 131, 143, 144, 147, 154, 163, 170, 187, 198, 200, 205, 210, 212, 221, 227, 238, 240, 253, 255, 260, 262, 265, 271, 275
Offset: 1

Views

Author

Paolo P. Lava and Giorgio Balzarotti, Oct 30 2007

Keywords

Examples

			13^3=2197 and 2+1+9+7=19 is prime.

Links

Crossrefs

Cf. A076203, A134532, A134533, A134534.

Programs

  • Maple
    P:=proc(n) local cont,i,k,w; if isprime(n) then cont:=0; while cont<1000 do cont:=cont+1; w:=0; k:=n^cont; while k>0 do w:=w+k-(trunc(k/10)*10); k:=trunc(k/10); od; if isprime(w) then print(cont); fi; od; fi; end: P(13);
  • Mathematica
    Select[Range[250], PrimeQ[Total[IntegerDigits[13^#]]]&] (* Vincenzo Librandi, Apr 17 2013 *)
Showing 1-3 of 3 results.

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

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