A176193 - OEIS

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A176193

The positions of semiprimes in A002808.

1

1, 2, 4, 5, 7, 8, 12, 13, 15, 16, 21, 22, 23, 25, 26, 31, 33, 35, 38, 40, 41, 43, 46, 49, 52, 55, 59, 61, 62, 63, 66, 68, 69, 70, 78, 81, 84, 87, 88, 90, 91, 92, 97, 100, 101, 106, 107, 108, 110, 111, 118, 120, 121, 123, 127, 129, 136, 137, 140, 142, 144, 149, 154, 155

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OFFSET

1,2

LINKS

Robert Israel, Table of n, a(n) for n = 1..10000

FORMULA

a(n) = A001358(n) - A000720(A001358(n)) - 1.

MAPLE

SP:= select(t -> numtheory:-bigomega(t) = 2, [$1..1000]):

map(t -> t - 1 - numtheory:-pi(t), SP); # Robert Israel, Jan 08 2024

CROSSREFS

Cf. A000720, A001358, A002808.

Sequence in context: A261188 A343267 A350417 * A072920 A330708 A107899

Adjacent sequences: A176190 A176191 A176192 * A176194 A176195 A176196

KEYWORD

nonn

AUTHOR

Juri-Stepan Gerasimov, Apr 11 2010

EXTENSIONS

Corrected (22, 41 inserted, 85 replaced by 87 etc.) by R. J. Mathar, Apr 13 2010

STATUS

approved