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.

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A109958 Concatenate n and the sum of primes dividing n (counting multiplicity).

Original entry on oeis.org

10, 22, 33, 44, 55, 65, 77, 86, 96, 107, 1111, 127, 1313, 149, 158, 168, 1717, 188, 1919, 209, 2110, 2213, 2323, 249, 2510, 2615, 279, 2811, 2929, 3010, 3131, 3210, 3314, 3419, 3512, 3610, 3737, 3821, 3916, 4011, 4141, 4212, 4343, 4415, 4511, 4625, 4747
Offset: 1

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Author

Jason Earls, Jul 06 2005

Keywords

Crossrefs

Programs

  • Maple
    f:= proc(n) local q;
    q:= add(t[1]*t[2],t=ifactors(n)[2]);
    10^(1+ilog10(q))*n+q
    end proc:
    f(1):= 10:
    map(f, [$1..100]); # Robert Israel, Jun 26 2018
  • Mathematica
    pr[{a_,b_}]:=a*b;Join[{10},Table[FromDigits[Flatten[IntegerDigits[Join[{n},{Total[pr/@FactorInteger[n]]}]]]],{n,2,47}]] (* James C. McMahon, Apr 02 2024 *)

Formula

a(n) = 10^(A055652(A001414(n)))*n+A001414(n). - Robert Israel, Jun 26 2018
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