A340104 Products of distinct primes of nonprime index (A007821).

1, 2, 7, 13, 14, 19, 23, 26, 29, 37, 38, 43, 46, 47, 53, 58, 61, 71, 73, 74, 79, 86, 89, 91, 94, 97, 101, 103, 106, 107, 113, 122, 131, 133, 137, 139, 142, 146, 149, 151, 158, 161, 163, 167, 173, 178, 181, 182, 193, 194, 197, 199, 202, 203, 206, 214, 223, 226

Offset

1,2

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.

Links

Table of n, a(n) for n=1..58.

Formula

Equals A005117 /\ A320628.

Example

The sequence of terms together with the corresponding prime indices of prime indices begins:
     1: {}              58: {{},{1,3}}        113: {{1,2,3}}
     2: {{}}            61: {{1,2,2}}         122: {{},{1,2,2}}
     7: {{1,1}}         71: {{1,1,3}}         131: {{1,1,1,1,1}}
    13: {{1,2}}         73: {{2,4}}           133: {{1,1},{1,1,1}}
    14: {{},{1,1}}      74: {{},{1,1,2}}      137: {{2,5}}
    19: {{1,1,1}}       79: {{1,5}}           139: {{1,7}}
    23: {{2,2}}         86: {{},{1,4}}        142: {{},{1,1,3}}
    26: {{},{1,2}}      89: {{1,1,1,2}}       146: {{},{2,4}}
    29: {{1,3}}         91: {{1,1},{1,2}}     149: {{3,4}}
    37: {{1,1,2}}       94: {{},{2,3}}        151: {{1,1,2,2}}
    38: {{},{1,1,1}}    97: {{3,3}}           158: {{},{1,5}}
    43: {{1,4}}        101: {{1,6}}           161: {{1,1},{2,2}}
    46: {{},{2,2}}     103: {{2,2,2}}         163: {{1,8}}
    47: {{2,3}}        106: {{},{1,1,1,1}}    167: {{2,6}}
    53: {{1,1,1,1}}    107: {{1,1,4}}         173: {{1,1,1,3}}

Mathematica

Select[Range[100], SquareFreeQ[#]&&FreeQ[If[#==1, {}, FactorInteger[#]], {p_, k_}/; PrimeQ[PrimePi[p]]]&]

Crossrefs

These primes (of nonprime index) are listed by A007821.

The non-strict version is A320628, with odd case A320629.

The odd case is A340105.

The prime instead of nonprime version:

primes: A006450

products: A076610

strict: A302590

The semiprime instead of nonprime version:

primes: A106349

products: A339112

strict: A340020

The squarefree semiprime instead of nonprime version:

strict: A309356

primes: A322551

products: A339113

A056239 gives the sum of prime indices, which are listed by A112798.

A257994 counts prime prime indices.

A302242 is the weight of the multiset of multisets with MM-number n.

A305079 is the number of connected components for MM-number n.

A320911 lists products of squarefree semiprimes (Heinz numbers of A338914).

A320912 lists products of distinct semiprimes (Heinz numbers of A338916).

A330944 counts nonprime prime indices.

A330945 lists numbers with a nonprime prime index (nonprime case: A330948).

A339561 lists products of distinct squarefree semiprimes (A339560).

MM-numbers: A255397 (normal), A302478 (set multisystems), A320630 (set multipartitions), A302494 (sets of sets), A305078 (connected), A316476 (antichains), A318991 (chains), A320456 (covers), A328514 (connected sets of sets), A329559 (clutters), A340019 (half-loop graphs).

Cf. A000040, A000720, A001055, A001222, A003963, A005117, A007097, A018252, A289509, A320461, A320631.

Sequence in context: A130710 A145300 A240029 * A216525 A232637 A333383

Adjacent sequences: A340101 A340102 A340103 * A340105 A340106 A340107

Keyword

nonn

Author

Gus Wiseman, Mar 12 2021

Status

approved