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A280383 Numbers n such that n-1 has the same count of prime factors as n+1 when including multiplicity and also when not. 3
4, 6, 12, 18, 19, 30, 34, 42, 51, 55, 56, 60, 72, 86, 92, 94, 102, 108, 138, 142, 144, 150, 160, 180, 184, 186, 192, 198, 202, 204, 214, 216, 218, 220, 228, 236, 240, 243, 248, 249, 266, 270, 282, 300, 302, 304, 307, 312, 320, 322, 328, 340, 341, 348, 349, 392, 394, 412, 414, 416, 420, 424, 432, 446, 452, 462, 470, 472, 476, 491, 516, 518, 522, 534, 536, 544, 552, 570, 580, 582, 590, 600, 604, 618, 634, 638, 642, 660, 664, 668, 670, 680, 686, 688, 696, 698, 701, 722 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

First differs from its subsequence A074997 at a(97) = 701 because A074997(97) = 722.

LINKS

Rick L. Shepherd, Table of n, a(n) for n = 1..10000

FORMULA

Sequence is A088070 INTERSECT A280382.

EXAMPLE

The number 19 is a term because 18 = 2*3^2 and 20 = 2^2*5 each have two distinct prime factors and each have three prime factors when counted with multiplicity.

PROG

(PARI) IsInA280383(n) = n > 1 && bigomega(n-1) == bigomega(n+1) && omega(n-1) == omega(n+1)

CROSSREFS

Cf. A001221, A001222, A074997, A088070, A280382.

Sequence in context: A301166 A310599 A074997 * A045959 A310600 A296507

Adjacent sequences:  A280380 A280381 A280382 * A280384 A280385 A280386

KEYWORD

nonn

AUTHOR

Rick L. Shepherd, Jan 02 2017

STATUS

approved

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Last modified November 22 02:58 EST 2019. Contains 329383 sequences. (Running on oeis4.)