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A074174 Smallest number k such that k and k+n are of the form p^2*q where p and q are primes. 3
44, 18, 172, 171, 45, 12, 45, 12, 236, 18, 52, 63, 50, 261, 524, 12, 28, 45, 44, 637, 404, 28, 45, 20, 20, 18, 18, 147, 63, 20, 44, 12, 12, 18, 28, 63, 116, 12, 236, 12, 75, 50, 20, 325, 18, 52, 28, 20, 50, 18, 12, 423, 45, 44, 20, 12, 18, 18, 116, 147, 63, 325, 12, 12, 52 (list; graph; refs; listen; history; internal format)
OFFSET

1,1

EXAMPLE

a(2) = 18 as 18 = 3^2*2 and 18 +2 =20 = 2^2*5.

MATHEMATICA

Table[k=1; found=False; While[ !found, k++; f1=FactorInteger[k]; If[Sort[Transpose[f1][[2]]]=={1, 2}, f2=FactorInteger[k+n]; If[Sort[Transpose[f2][[2]]]=={1, 2}, found=True]]]; k, {n, 100}]

CROSSREFS

Cf. A074172, A074173, A054753.

Sequence in context: A169857 A160330 A074175 * A033977 A033364 A108213

Adjacent sequences:  A074171 A074172 A074173 * A074175 A074176 A074177

KEYWORD

nonn

AUTHOR

Amarnath Murthy (amarnath_murthy(AT)yahoo.com), Aug 30 2002

EXTENSIONS

Corrected and extended by T. D. Noe (noe(AT)sspectra.com), Oct 04 2004

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Last modified February 15 11:25 EST 2012. Contains 205777 sequences.