A217048 Semiprimes using only the curved digits 0, 3, 6, 8 and 9.

6, 9, 33, 38, 39, 69, 86, 93, 303, 309, 339, 386, 393, 398, 633, 669, 689, 698, 699, 803, 838, 866, 869, 886, 889, 893, 898, 899, 933, 939, 989, 993, 998, 3039, 3063, 3086, 3093, 3098, 3099, 3309, 3338, 3369, 3383, 3386, 3398, 3603, 3639, 3669, 3683, 3693

Offset: 1

Author

Jonathan Vos Post, Sep 25 2012

Keywords

• nonn
• base
• easy

Comments

This is to A079652 as semiprimes A001358 are to primes A000040.

Examples

			a(41) = 3338 = 2 * 1669, the 938th semiprime.
		

Links

• Robert Israel, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A001358, A072960.

Programs

Magma

IsSemiprime:=func; [n: n in [2..3700] | IsSemiprime(n) and Intseq(n) subset [0,3,6,8,9]]; // Bruno Berselli, Sep 25 2012

Maple

R:= [0,3,6,8,9]:
Res:= NULL: count:= 0:
for m from 1 while count < 100 do
  L:= convert(m,base,5);
  n:= add(R[L[i]+1]*10^(i-1),i=1..nops(L));
  if numtheory:-bigomega(n)=2 then Res:= Res, n; count:= count+1 fi
od:
Res; # Robert Israel, Feb 16 2020

Formula

A001358 INTERSECTION A072960.