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A178313 Absolute difference between prime factors of n-th semiprime mod n. 2
0, 1, 0, 3, 0, 2, 4, 1, 0, 1, 8, 3, 2, 3, 10, 5, 0, 14, 6, 16, 6, 7, 8, 20, 10, 4, 12, 12, 12, 26, 6, 28, 12, 14, 16, 34, 18, 19, 10, 0, 18, 38, 40, 12, 20, 44, 22, 2, 24, 21, 26, 25, 50, 16, 26, 0, 56, 29, 58, 32, 6, 33, 1, 35, 22, 36, 34, 8, 68, 35, 38, 24, 34, 70, 4, 35, 42, 76, 6, 0 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,4

LINKS

Alois P. Heinz, Table of n, a(n) for n = 1..20000

EXAMPLE

a(2)=1 because semiprime(2)=6=3*2 and ((3-2) mod 2)=1.

MATHEMATICA

semiPrimeQ[n_] := Plus @@ Last /@ FactorInteger@ n == 2; f[n_] := Subtract @@ Reverse@ Flatten[ Table[ #[[1]], {#[[2]]}] & /@ FactorInteger@ n]; t = Select[ Range@ 215, semiPrimeQ]; Table[ Mod[ f[ t[[n]]], n], {n, 80}]

CROSSREFS

Cf. A001358, A178102, A109313.

Sequence in context: A112974 A113069 A136163 * A190013 A171088 A058624

Adjacent sequences:  A178310 A178311 A178312 * A178314 A178315 A178316

KEYWORD

nonn

AUTHOR

Juri-Stepan Gerasimov, Dec 20 2010

STATUS

approved

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Last modified September 22 07:34 EDT 2020. Contains 337289 sequences. (Running on oeis4.)