A086698 Two-sided semiprimes: deleting any number of digits at left or at right, but not both, leaves a semiprime.

4, 6, 9, 46, 49, 69, 94, 469, 626, 694, 914, 934, 939, 949, 4694, 4934, 4939, 9134, 9346, 9586, 62386, 62614, 91346, 959939, 6998339, 91439939

Offset

1,1

Links

Table of n, a(n) for n=1..26.

Example

a(18)=9134 is a term because 9134, 913,134,34,91,4,9 all are semiprimes.

Mathematica

aspQ[n_]:=Module[{idn=IntegerDigits[n]}, AllTrue[Union[FromDigits/@Join[NestList[Rest[#]&, idn, Length[idn]-1], NestList[Most[#]&, idn, Length[idn]-1]]], PrimeOmega[#]==2&]]; Select[Range[10^6], aspQ] (* The program generates the first 24 terms of the sequence. *) (* Harvey P. Dale, Sep 04 2025 *)

Crossrefs

Sequence in context: A085733 A242751 A107342 * A317248 A115666 A245044

Adjacent sequences: A086695 A086696 A086697 * A086699 A086700 A086701

Keyword

base,fini,full,nonn

Author

Shyam Sunder Gupta, Jul 28 2003

Status

approved