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.

A325994 Heinz numbers of integer partitions such that not every ordered pair of distinct parts has a different quotient.

Original entry on oeis.org

42, 84, 126, 168, 210, 230, 252, 294, 336, 378, 390, 399, 420, 460, 462, 504, 546, 588, 630, 672, 690, 714, 742, 756, 780, 798, 840, 882, 920, 924, 966, 1008, 1050, 1092, 1134, 1150, 1170, 1176, 1197, 1218, 1260, 1302, 1344, 1365, 1380, 1386, 1428, 1470, 1484
Offset: 1

Views

Author

Gus Wiseman, Jun 02 2019

Keywords

Comments

The Heinz number of an integer partition (y_1,...,y_k) is prime(y_1)*...*prime(y_k).

Examples

			The sequence of terms together with their prime indices begins:
    42: {1,2,4}
    84: {1,1,2,4}
   126: {1,2,2,4}
   168: {1,1,1,2,4}
   210: {1,2,3,4}
   230: {1,3,9}
   252: {1,1,2,2,4}
   294: {1,2,4,4}
   336: {1,1,1,1,2,4}
   378: {1,2,2,2,4}
   390: {1,2,3,6}
   399: {2,4,8}
   420: {1,1,2,3,4}
   460: {1,1,3,9}
   462: {1,2,4,5}
   504: {1,1,1,2,2,4}
   546: {1,2,4,6}
   588: {1,1,2,4,4}
   630: {1,2,2,3,4}
   672: {1,1,1,1,1,2,4}
		

Crossrefs

The subset case is A325860.
The maximal case is A325861.
The integer partition case is A325853.
The strict integer partition case is A325854.
Heinz numbers of the counterexamples are given by A325994.

Programs

  • Mathematica
    Select[Range[1000],!UnsameQ@@Divide@@@Subsets[PrimePi/@First/@FactorInteger[#],{2}]&]