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A255013 a(n) = the least semiprime such that n+a(n) is also semiprime. 0
9, 4, 6, 6, 4, 4, 14, 6, 6, 4, 4, 9, 9, 21, 6, 6, 4, 4, 6, 6, 4, 4, 10, 9, 9, 9, 6, 6, 4, 4, 4, 6, 6, 4, 4, 10, 9, 39, 10, 6, 10, 4, 6, 14, 4, 9, 4, 9, 6, 15, 4, 6, 4, 4, 10, 6, 25, 4, 6, 9, 4, 15, 6, 10, 4, 21, 10, 6, 22, 4, 6, 10, 4, 21, 10, 6, 9, 4, 6, 6, 4, 4, 4, 9, 6, 9, 4, 6, 4, 4, 4, 14 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Corresponding values of n+a(n): 10,6,9,10,9,10,21,14,15,14,15,21,22,35,21.

LINKS

Table of n, a(n) for n=1..92.

EXAMPLE

a(1)=9 because 1+9=10=2*5, a(2)=4 because 2+4=6=2*3.

MATHEMATICA

Table[m=4; While[2!=PrimeOmega[m]||2!=PrimeOmega[m+n], m++]; m, {n, 100}]

CROSSREFS

Cf. A001358.

Sequence in context: A194826 A309610 A198989 * A088539 A245084 A199054

Adjacent sequences:  A255010 A255011 A255012 * A255014 A255015 A255016

KEYWORD

nonn

AUTHOR

Zak Seidov, Feb 12 2015

STATUS

approved

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Last modified August 22 05:00 EDT 2019. Contains 326172 sequences. (Running on oeis4.)