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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.

A325097 Heinz numbers of integer partitions whose distinct parts have no binary carries.

Original entry on oeis.org

1, 2, 3, 4, 5, 6, 7, 8, 9, 11, 12, 13, 14, 16, 17, 18, 19, 21, 23, 24, 25, 26, 27, 28, 29, 31, 32, 33, 35, 36, 37, 38, 41, 42, 43, 47, 48, 49, 52, 53, 54, 56, 57, 58, 59, 61, 63, 64, 67, 69, 71, 72, 73, 74, 76, 79, 81, 83, 84, 86, 89, 95, 96, 97, 98, 99, 101
Offset: 1

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Author

Gus Wiseman, Mar 27 2019

Keywords

Comments

A binary carry of two positive integers is an overlap of the positions of 1's in their reversed binary expansion.
The Heinz number of an integer partition (y_1,...,y_k) is prime(y_1) * ... * prime(y_k), so these are numbers whose distinct prime indices have no binary carries.

Examples

			Most small numbers are in the sequence, however the sequence of non-terms together with their prime indices begins:
  10: {1,3}
  15: {2,3}
  20: {1,1,3}
  22: {1,5}
  30: {1,2,3}
  34: {1,7}
  39: {2,6}
  40: {1,1,1,3}
  44: {1,1,5}
  45: {2,2,3}
  46: {1,9}
  50: {1,3,3}
  51: {2,7}
  55: {3,5}
  60: {1,1,2,3}
  62: {1,11}
  65: {3,6}
  66: {1,2,5}
  68: {1,1,7}
  70: {1,3,4}
		

Crossrefs

Programs

  • Mathematica
    binpos[n_]:=Join@@Position[Reverse[IntegerDigits[n,2]],1];
    stableQ[u_,Q_]:=!Apply[Or,Outer[#1=!=#2&&Q[#1,#2]&,u,u,1],{0,1}];
    Select[Range[100],stableQ[PrimePi/@First/@FactorInteger[#],Intersection[binpos[#1],binpos[#2]]!={}&]&]