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.

A254859 Numbers that are both a sum and a product of two or more consecutive primes.

Original entry on oeis.org

15, 30, 77, 143, 210, 221, 323, 1001, 2310, 4199, 5767, 7429, 9797, 10403, 11021, 12317, 20711, 22499, 23707, 25591, 28891, 30030, 33263, 34571, 36863, 38021, 46189, 47053, 75067, 77837, 79523, 82861, 82919, 89951, 95477, 99221, 104927, 111547, 116939, 136891, 141367, 145157, 146969, 154433
Offset: 1

Views

Author

Altug Alkan, May 05 2016

Keywords

Examples

			15 is a term because 15 = 3 + 5 + 7 = 3*5.
30 is a term because 30 = 13 + 17 = 2*3*5.
77 is a term because 77 = 2 + 3 + 5 + 7 + 11 + 13 + 17 + 19 = 7*11.
		

Crossrefs

Intersection of A050936 and A097889.

Programs

  • Mathematica
    np = NextPrime; pro[n_] := Block[{e, f}, {f, e} = Transpose@ FactorInteger@ n; Length@ f > 1 && Union@ e == {1} && np@ Most@ f == Rest@ f]; seq[lim_] := Union[Reap[Block[{p = 2, q, s}, While[2 p < lim, q = np@p; s = p+q; While[s <= lim, If[pro@s, Sow@s]; q = np@q; s += q]; p = np@p]]][[2, 1]]]; seq[10^5] (* Giovanni Resta, May 05 2016 *)
  • Python
    # see link