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A332035
Indices of A004394(n) in A055932.
2
1, 2, 3, 4, 6, 9, 12, 13, 15, 21, 26, 30, 36, 49, 53, 63, 72, 86, 114, 149, 175, 212, 221, 285, 367, 424, 505, 541, 643, 687, 703, 886, 1015, 1198, 1272, 1496, 1586, 1704, 2116, 2491, 2912, 3076, 3587, 3791, 4052, 4971, 5999, 6087, 6845, 6955, 7330, 8481, 8933
OFFSET
1,2
COMMENTS
A055932 lists numbers m whose prime divisors p are consecutive primes starting with 2, while A004394 is a subset of A025487, the latter lists numbers m that are products of primorials. With both, we find a range of indices of primes 1, 2, ..., k that divide m. While A055932 admits any multiplicity for primes regardless of their index, the latter only admits decreasing multiplicities as prime index k increases. A004394 is a subset of A025487, which is in turn a subset of A055932.
LINKS
MATHEMATICA
Block[{s = TakeWhile[Import["https://oeis.org/A055932/b055932.txt", "Data"], Length@ # > 0 &][[All, -1]], t = Join @@ {Map[ToExpression@ Last@ StringSplit@ # &, #1][[All, -1]], Map[Times @@ Flatten@ {Complement[#1, Union[#2, #3]], Product[Prime@ i, {i, PrimePi@ #}] & /@ #2, Factorial /@ #3} & @@ ToExpression@ {StringSplit[#, _?(! DigitQ@ # &)], StringCases[#, (x : DigitCharacter ..) ~~ "#" :> x], StringCases[#, (x : DigitCharacter ..) ~~ "!" :> x]} &@ Last@ StringSplit[First[#]] &, TakeWhile[#2, Length@ # > 0 &]]} & @@ TakeDrop[Drop[#, 3] &@ Import["https://oeis.org/A004394/b004394.txt", "Data"], 2000] }, Reap[Do[Which[Length@ t == 0, Break[], First[t] == s[[i]] , t = Rest@ t; Sow[i]], {i, Length@ s}]][[-1, -1]]]
CROSSREFS
Cf. A004394, A025487, A055932, A293635 (Indices of A004394(n) in A025487), A332034.
Sequence in context: A377151 A288734 A332034 * A318759 A018471 A240307
KEYWORD
nonn
AUTHOR
Michael De Vlieger, Feb 05 2020
STATUS
approved