A103397 Semiprimes in A103377.

4, 9, 15, 21, 33, 38, 58, 65, 86, 106, 121, 129, 265, 511, 8114, 8193, 16307, 16853, 17855, 19857, 31298, 68037, 104739, 124205, 131209, 134149, 140457, 152849, 252914, 259918, 265358, 274606, 417527, 2498871, 5291863, 8424051, 8743821

Offset

1,1

Links

Table of n, a(n) for n=1..37.

Formula

Intersection of A103377 with A001358.

Example

2071468241 is an element of A103377 and 2071468241= 17 * 121851073 which shows that it is a semiprime.

Mathematica

SemiprimeQ[n_]:=Plus@@FactorInteger[n][[All, 2]]?2; Clear[a]; k=9; Do[a[n]=1, {n, k+1}]; a[n_]:=a[n]=a[n-k]+a[n-k-1]; A103377=Array[a, 100] A103387=Union[Select[Array[a, 1000], PrimeQ]] A103397=Union[Select[Array[a, 300], SemiprimeQ]] N[Solve[x^10 - x - 1 == 0, x], 111][[2]]

Crossrefs

Cf. A001358, A000931, A079398, A103372-103381, A103377, A103397.

Sequence in context: A103400 A103399 A103398 * A103394 A103395 A103393

Adjacent sequences: A103394 A103395 A103396 * A103398 A103399 A103400

Keyword

easy,nonn

Author

Jonathan Vos Post, Feb 15 2005

Status

approved