A051266 - OEIS

A051266

Numbers n such that maximal value of prime divisors of reduced residue system for n is 2.

7, 11, 13, 15, 16, 17, 19, 21, 22, 23, 25, 26, 27, 28, 29, 32, 33, 34, 35, 36, 38, 39, 40, 44, 45, 46, 48, 50, 51, 52, 54, 56, 57, 58, 62, 63, 64, 66, 68, 69, 70, 72, 74, 75, 76, 78, 80, 82, 84, 86, 88, 90, 92, 94, 96, 98, 100, 102, 104, 105, 108, 110, 112, 114, 120, 126

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OFFSET

1,1

COMMENTS

Largest value of A001221(k) = 2 for 1 <= k <= n such that gcd (k, n) = 1, i.e., k in row n of A038566. - Michael De Vlieger, Aug 10 2017

LINKS

Michael De Vlieger, Table of n, a(n) for n = 1..161

EXAMPLE

n = 29 is here because for terms of RRS(29) = {1, 2, ..., 27, 28} the number of prime divisors is 0(for 1), 1(for prime powers) or 2 (for 6, 10, 12, 14, 15, 18, 20, 21, 22, 24, 26, 28).

MATHEMATICA

Block[{n = 2, P}, P = Product[Prime@ i, {i, n}]; P + Position[#, n][[All, 1]] &@ Array[Max@ Map[PrimeNu, Cases[Range@ #, k_ /; CoprimeQ[#, k]]] &, 120, P + 1]] (* Michael De Vlieger, Aug 10 2017 *)

CROSSREFS

Cf. A001221, A002110, A038566, A048597, A051250, A051265, A051267, A051268.

Sequence in context: A337459 A245178 A287161 * A370007 A172247 A374082

Adjacent sequences: A051263 A051264 A051265 * A051267 A051268 A051269

KEYWORD

nonn

AUTHOR

Labos Elemer

STATUS

approved