A074174 Smallest number k such that k and k+n are of the form p^2*q where p and q are primes.

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

Offset

1,1

Links

Harvey P. Dale, Table of n, a(n) for n = 1..1000

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}]
snk[n_]:=Module[{k=1}, While[Sort[FactorInteger[k][[All, 2]]]!={1, 2} || Sort[FactorInteger[k+n][[All, 2]]]!={1, 2}, k++]; k]; Array[snk, 70]

Crossrefs

Cf. A074172, A074173, A054753.

Sequence in context: A371554 A160330 A074175 * A033977 A033364 A108213

Adjacent sequences: A074171 A074172 A074173 * A074175 A074176 A074177

Keyword

nonn

Author

Amarnath Murthy, Aug 30 2002

Extensions

Corrected and extended by T. D. Noe, Oct 04 2004

Status

approved