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.

A139752 Primes arising in A139750.

Original entry on oeis.org

2, 3, 5, 7, 2, 5, 17, 37, 2, 3, 11, 83, 3, 7, 19, 67, 5, 13, 29, 53, 5, 41
Offset: 1

Views

Author

Ctibor O. Zizka, May 19 2008

Keywords

A178357 Numbers n such that d(1)^1 + d(2)^2 +...+ d(p)^p and d(1)^p + d(2)^p-1 +...+ d(p)^1 are prime numbers, where d(i), i=1..p, are the digits of n.

Original entry on oeis.org

2, 3, 5, 7, 11, 12, 14, 16, 21, 23, 29, 32, 34, 38, 41, 43, 47, 56, 61, 65, 74, 83, 89, 92, 98, 101, 110, 111, 113, 115, 120, 122, 131, 133, 137, 139, 140, 146, 153, 155, 160, 164, 182, 186, 188, 191, 203, 205, 212, 214, 221, 225, 227, 230, 232, 236, 272, 281, 287, 290, 302, 304, 311, 313, 319, 320, 326, 331
Offset: 1

Views

Author

Michel Lagneau, Dec 21 2010

Keywords

Examples

			1583 is in the sequence because :
1 + 5^2 + 8^3 + 3^4 = 619 and 1^4 + 5^3 + 8^2 + 3^1 = 193 are prime numbers.
		

Crossrefs

Programs

  • Maple
    with(numtheory):for n from 1 to 1000 do:l:=length(n):n0:=n:s1:=0:s2:=0:for
      m from 1 to l do:q:=n0:u:=irem(q,10):v:=iquo(q,10):n0:=v :s1:=s1+u^(l-m+1):s2:=s2+u^m:od:
      if type(s1,prime)=true and type(s2,prime)=true then printf(`%d, `,n):else fi:od:
  • Mathematica
    okQ[n_] := Module[{d=IntegerDigits[n], r}, r=Length[d]; PrimeQ[Total[d^Range[r]]] && PrimeQ[Total[d^Range[r, 1, -1]]]]; Select[Range[1000], okQ]

A140281 A Diophantine equation over digits of n. Numbers n such that x_1/r +x_2/r-1 + ... + x_r/1 = k; x_i digits of n; k integer.

Original entry on oeis.org

0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 300, 301, 302, 303, 304, 305, 306, 307, 308, 309, 320, 321, 322, 323, 324, 325, 326
Offset: 0

Views

Author

Ctibor O. Zizka, May 23 2008

Keywords

Examples

			n=321 : 3/3 + 2/2 + 1/1 = 3, 321 belongs to the sequence
		

Crossrefs

Programs

  • Mathematica
    Join[{0},Select[Range[400],IntegerQ[Total[IntegerDigits[#]/Reverse[ Range[ IntegerLength[ #]]]]]&]] (* Harvey P. Dale, May 17 2016 *)
Showing 1-3 of 3 results.