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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A140460 a(0) = 2; thereafter a(n) = smallest integer not a multiple of an earlier terms nor a sum of two earlier terms.

Original entry on oeis.org

2, 3, 7, 11, 17, 23, 29, 37, 41, 47, 53, 59, 65, 71, 79, 83, 89, 95, 101, 107, 113, 125, 131, 137, 149, 155, 163, 167, 173, 179, 191, 197, 211, 215, 223, 227, 233, 239, 247, 251, 257, 263, 269, 277, 281, 293, 305, 311, 317, 331, 335
Offset: 0

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Author

Russell Y. Webb (r.webb(AT)elec.canterbury.ac.nz), Jul 22 2008

Keywords

Comments

Note that the first composite value is a(12) = 65 = 5 * 13, since 5 and 13 are the first two primes sieved out of the sequence. Similarly, the second composite value is a(17) = 95 = 5 * 19, since 5 and 19 are the first and third primes sieved out of the sequence. - Jonathan Vos Post, Jul 27 2008

Crossrefs

Programs

  • C
    #include 
    #include 
    void sieve(){ const int first = 2; const int max = 10000; bool member[max]; for(int i = first; i < max; ++i){ member[i] = true; } for(int i = first; i < max; ++i){ if(member[i]){ for(int x = i + i; x < max; x += i){ member[x] = false; } for(int j = first; j < i; ++j){ if(member[j] && i + j < max){ member[i + j] = false; } } } } int num = 0; for(int i = first; i < max; ++i){ if(member[i]){ printf("%i, ", i); num += 1; } } printf(" num = %i ", num); }
  • Mathematica
    s={2};Do[m=2;Until[Total[Boole[Divisible[m,s]]]==0&&!MemberQ[Total/@Subsets[s,{2}],m],m++];AppendTo[s,m],{n,50}];s (* James C. McMahon, Jul 09 2025 *)
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