A144585 - OEIS

A144585

Composites whose sum of prime factors is an odd nonprime (counted with multiplicity).

14, 20, 24, 26, 27, 38, 44, 46, 62, 68, 74, 86, 92, 94, 105, 106, 112, 116, 122, 124, 125, 126, 134, 146, 150, 152, 158, 160, 164, 166, 171, 178, 180, 188, 192, 194, 195, 206, 208, 212, 216, 218, 226, 231, 232, 234, 236, 243, 244, 254, 255, 261, 262, 272, 275

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OFFSET

1,1

LINKS

Table of n, a(n) for n=1..55.

EXAMPLE

14 is a term because 14 = 2*7 and 2+7 = 9 (an odd nonprime);

20 is a term because 20 = 2*2*5 and 2+2+5 = 9,

24 is a term because 24 = 2*2*2*3 and 2+2+2+3 = 9;

26 is a term because 26 = 2*13 and 2+13 = 15 (also an odd nonprime).

MAPLE

ifac := proc (n) local L, x: L := ifactors(n)[2]: map(proc (x) options operator, arrow: seq(x[1], j = 1 .. x[2]) end proc, L) end proc: a := proc (n) local b: b := add(ifac(n)[j], j = 1 .. nops(ifac(n))): if isprime(n) = false and `mod`(b, 2) = 1 and isprime(b) = false then n else end if end proc: seq(a(n), n = 1 .. 280); # Emeric Deutsch, Jan 27 2009

CROSSREFS

Cf. A002808, A036349, A046363, A141468.

Sequence in context: A074851 A193672 A087678 * A186193 A285426 A108874

Adjacent sequences: A144582 A144583 A144584 * A144586 A144587 A144588

KEYWORD

nonn

AUTHOR

Juri-Stepan Gerasimov, Jan 04 2009

EXTENSIONS

Corrected (removed 81; added 126, 158) and extended by Emeric Deutsch, Jan 27 2009

Example section edited by Jon E. Schoenfield, Jan 15 2019

STATUS

approved