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.

A079131 Primes such that iterated sum-of-digits (A038194) is odd.

Original entry on oeis.org

3, 5, 7, 19, 23, 37, 41, 43, 59, 61, 73, 79, 97, 109, 113, 127, 131, 149, 151, 163, 167, 181, 199, 223, 239, 241, 257, 271, 277, 293, 307, 311, 313, 331, 347, 349, 367, 379, 383, 397, 401, 419, 421, 433, 439, 457, 487, 491, 509, 523, 541, 547, 563, 577, 599
Offset: 1

Views

Author

Klaus Brockhaus, Dec 28 2002

Keywords

Comments

Subsequence of primes of A187318. - Michel Marcus, Jun 08 2015
Primes congruent to 1, 3, 5, 7 mod 18. - Robert Israel, Jun 08 2015

Links

Crossrefs

Cf. A038194, A078403, A079130, A079132, A187318.

Programs

  • Magma
    [p: p in PrimesUpTo(600) | p mod 18 in [1,3,5,7]]; // Vincenzo Librandi, Jun 07 2015
  • Magma
    [a: n in [0..1000] | IsPrime(a) where a is Floor(9*n/5)]; // Vincenzo Librandi, Jun 08 2015
  • Maple
    select(isprime, [3, seq(seq(i*18+j, j=[1,5,7]),i=0..100)]); # Robert Israel, Jun 08 2015
  • Mathematica
    Select[Prime[Range[120]], OddQ[Mod[#, 9]] &] (* Bruno Berselli, Aug 31 2012 *)
  • PARI
    forprime(p=2,600,if((p%9)%2==1,print1(p,",")))

A079132 Primes such that iterated sum-of-digits (A038194) is even.

Original entry on oeis.org

2, 11, 13, 17, 29, 31, 47, 53, 67, 71, 83, 89, 101, 103, 107, 137, 139, 157, 173, 179, 191, 193, 197, 211, 227, 229, 233, 251, 263, 269, 281, 283, 317, 337, 353, 359, 373, 389, 409, 431, 443, 449, 461, 463, 467, 479, 499, 503, 521, 557, 569, 571, 587, 593, 607
Offset: 1

Views

Author

Klaus Brockhaus, Dec 28 2002

Keywords

Crossrefs

Cf. A078403, A079130, A079131.

Programs

  • Mathematica
    Select[Prime[Range[120]], EvenQ[Mod[#, 9]] &] (* Bruno Berselli, Aug 31 2012 *)
  • PARI
    forprime(p=2,600,if((p%9)%2==0,print1(p,",")))

A290944 Primes p such that sum of digits of p^3 is a perfect square.

Original entry on oeis.org

3, 1753, 1999, 2389, 2713, 3301, 3361, 3529, 3583, 3607, 3631, 3643, 3697, 3889, 3907, 4093, 4099, 4129, 4153, 4159, 4243, 4423, 4591, 4639, 4813, 5167, 5449, 5503, 5527, 5563, 5683, 5689, 5827, 6199, 6211, 6427, 6529, 6553, 6691, 6709, 6883, 6949, 6961, 6997
Offset: 1

Views

Author

K. D. Bajpai, Aug 14 2017

Keywords

Comments

All the terms in this sequence, except a(1), are congruent to 1 mod 3.
After a(1), all the terms are congruent to {1, 4, 7} mod 9.

Examples

			a(1) = 3 is prime: 3^3 = 27; 2 + 7 = 9 = 3^2.
a(2) = 1753 is prime: 1753^3 = 5386984777; 5 + 3 + 8 + 6 + 9 + 8 + 4 + 7 + 7 + 7 = 64 = 8^2.

Links

Crossrefs

Cf. A007605, A052279, A079130, A086924, A235398, A259418, A290843.

Programs

  • Magma
    [p: p in PrimesUpTo(1000) | IsSquare(&+Intseq(p^3))];
  • Maple
    f:= n->add(d, d=convert(n^3, base, 10)):
select(t -> type(sqrt(f(t)), integer), [seq(ithprime(m), m=1..10^3)]);
  • Mathematica
    Select[Prime[Range[2000]], IntegerQ[Sqrt[Plus @@ IntegerDigits[#^3]]] &]
  • PARI
    forprime(p=1, 5000, if(issquare(sumdigits(p^3)), print1(p, ", ")));
  • PARI
    is(n) = ispseudoprime(n) && issquare(sumdigits(n^3)) \\ Felix Fröhlich, Aug 14 2017
Showing 1-3 of 3 results.

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

Content is available under The OEIS End-User License Agreement.