A371292 Numbers whose binary indices have prime indices covering an initial interval of positive integers.

0, 1, 2, 3, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 22, 23, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 86, 87, 92, 93, 94, 95, 112, 113, 114, 115, 116, 117, 118, 119

Offset: 0

Author

Gus Wiseman, Mar 27 2024

Keywords

• nonn
• base

Comments

A prime index of n is a number m such that prime(m) divides n. The multiset of prime indices of n is row n of A112798.

A binary index of n is any position of a 1 in its reversed binary expansion. The binary indices of n are row n of A048793.

Examples

			The terms together with their prime indices of binary indices begin:
   0: {}
   1: {{}}
   2: {{1}}
   3: {{},{1}}
   6: {{1},{2}}
   7: {{},{1},{2}}
   8: {{1,1}}
   9: {{},{1,1}}
  10: {{1},{1,1}}
  11: {{},{1},{1,1}}
  12: {{2},{1,1}}
  13: {{},{2},{1,1}}
  14: {{1},{2},{1,1}}
  15: {{},{1},{2},{1,1}}
  22: {{1},{2},{3}}
  23: {{},{1},{2},{3}}
  28: {{2},{1,1},{3}}
  29: {{},{2},{1,1},{3}}
  30: {{1},{2},{1,1},{3}}
  31: {{},{1},{2},{1,1},{3}}
  32: {{1,2}}
		

Links

• John Tyler Rascoe, Table of n, a(n) for n = 0..10000

Crossrefs

The case with squarefree product of prime indices is A371293.

For binary indices of each prime index we have A371447, A371448.

The connected components of this multiset system are counted by A371452.

A000009 counts partitions covering initial interval, compositions A107429.

A000670 counts patterns, ranked by A333217.

A011782 counts multisets covering an initial interval.

A048793 lists binary indices, A000120 length, A272020 reverse, A029931 sum.

A070939 gives length of binary expansion.

A131689 counts patterns by number of distinct parts.

Cf. A000040, A001222, A055887, A255906, A326782, A368109, A371291, A371294.

Programs

Mathematica

normQ[m_]:=m=={}||Union[m]==Range[Max[m]];
prix[n_]:=If[n==1,{},Flatten[Cases[FactorInteger[n], {p_,k_}:>Table[PrimePi[p],{k}]]]];
bpe[n_]:=Join@@Position[Reverse[IntegerDigits[n,2]],1];
Select[Range[0,100],normQ[Join@@prix/@bpe[#]]&]

Python

from itertools import count, islice
from sympy import sieve, factorint
def a_gen():
    for n in count(0):
        s = set()
        b = [(i+1) for i, x in enumerate(bin(n)[2:][::-1]) if x =='1']
        for i in b:
            p = factorint(i)
            for j in p:
                s.add(sieve.search(j)[0])
        x = sorted(s)
        y = len(x)
        if sum(x) == (y*(y+1))//2:
            yield n
A371292_list = list(islice(a_gen(), 65)) # John Tyler Rascoe, May 21 2024