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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A366673 a(n) is the least triprime k such that k + n is the next triprime after k.

Original entry on oeis.org

27, 18, 63, 8, 45, 12, 20, 130, 138, 154, 52, 30, 561, 78, 1194, 1930, 4277, 292, 5343, 26353, 4255, 7847, 34773, 18628, 71718, 72308, 168114, 64699, 43209, 227451, 239643, 17641, 97061, 162124, 924718, 930311, 488001, 7248711, 2986751, 704908, 4108654, 7220012
Offset: 1

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Author

Zak Seidov and Robert Israel, Oct 16 2023

Keywords

Examples

			a(3) = 63 because 63 = 3^2 * 7 is a triprime and the next triprime is 63 + 3 = 66 = 2 * 3 * 11.
		

Crossrefs

Programs

  • Maple
    T:= select(t -> numtheory:-bigomega(t) = 3, [$1..10^7]):
    dT:= T[2..-1]-T[1..-2]:
    V:= Vector(42):
    for i from 1 to nops(dT) do
      if dT[i] <= 42 and V[dT[i]] = 0 then V[dT[i]]:= T[i] fi
    od:
    convert(V,list);

A140784 a(n) = least member of A006881 whose difference from the following one equals n, or 0 if no such semiprime exists.

Original entry on oeis.org

14, 55, 35, 6, 46, 15, 26, 437, 146, 237, 95, 1082, 818, 597, 1603, 2705, 2078, 4511, 1418, 2681, 14545, 13863, 37551, 6559, 16053, 55805, 26707, 17965, 308918, 32777, 41222, 35103, 393565, 219509, 153263, 87627, 2263057, 35981, 1789339, 741841
Offset: 1

Views

Author

Philippe Lallouet (philip.lallouet(AT)orange.fr), Jul 13 2008

Keywords

Examples

			If psd(j) = A006881(j), psd(1)=6 and psd(2)=10, hence a(4)=6; psd(3) =14 and psd(4)=15, hence a(1)=14
		

Crossrefs

Extensions

Edited by N. J. A. Sloane, Jul 20 2008
Corrected a(21), a(22), a(36), extended by R. J. Mathar, Jul 23 2008

A176146 a(n) = n-th-semiprime without last digit.

Original entry on oeis.org

0, 0, 0, 1, 1, 1, 2, 2, 2, 2, 3, 3, 3, 3, 3, 4, 4, 5, 5, 5, 5, 6, 6, 6, 7, 7, 8, 8, 8, 8, 9, 9, 9, 9, 10, 11, 11, 11, 11, 12, 12, 12, 12, 13, 13, 14, 14, 14, 14, 14, 15, 15, 15, 16, 16, 16, 17, 17, 18, 18, 18, 19, 20, 20, 20, 20, 20, 20, 21, 21, 21, 21, 21, 21, 22, 22, 23, 23, 24, 24, 25
Offset: 1

Views

Author

Giovanni Teofilatto, Apr 10 2010

Keywords

Comments

Sequence A131109 shows that a(n+1)-a(n) can be larger than 1. [From T. D. Noe, Apr 12 2010]
The differences exceed 1 for the first time between a(186) = 59 and a(187) = 61. [R. J. Mathar, Apr 12 2010]

Crossrefs

Previous Showing 11-13 of 13 results.