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A114562 The first occurrence of n in A111701. 1
1, 4, 3, 8, 5, 36, 7, 16, 9, 20, 11, 72, 13, 28, 15, 32, 17, 108, 19, 40, 21, 44, 23, 144, 25, 52, 27, 56, 29, 900, 31, 64, 33, 68, 35, 216, 37, 76, 39, 80, 41, 252, 43, 88, 45, 92, 47, 288, 49, 100, 51, 104, 53, 324, 55, 112, 57, 116, 59, 1800, 61, 124, 63, 128, 65, 396, 67 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

A111701: Least integer obtained when n is divided by prime(1), then by prime(2), then by prime(3),..., stopping as soon as one of the primes does not divide it. In particular, a(2n-1) = 2n-1.

LINKS

Table of n, a(n) for n=1..67.

FORMULA

a(2n-1) = 2n-1, & a(2n) = k*4n for some k>0, if 2n == 0 (mod 3) then k = 3, if 2n ==0 (15 mod) k = 3*5, if 2n ==0 (105 mod) k = 3*5*7, if 2n ==0 (1155 mod) k = 3*5*7*11, etc.

MATHEMATICA

f[n_] := Block[{m = n, k = 1}, While[ IntegerQ[ m/Prime@k], m = m/Prime@k; k++ ]; m]; g[n_] := Block[{k = 1}, While[f@k != n, k++ ]; k]; Array[g, 67]

CROSSREFS

Cf. A111701, Complement of this sequence A095300.

Sequence in context: A082895 A086938 A007015 * A189042 A011451 A200089

Adjacent sequences:  A114559 A114560 A114561 * A114563 A114564 A114565

KEYWORD

nonn

AUTHOR

Robert G. Wilson v, Feb 04 2006

STATUS

approved

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Last modified March 23 02:39 EDT 2019. Contains 321422 sequences. (Running on oeis4.)