cp's OEIS Frontend

A082768 Numbers that begin with 1, 3, 7 or 9.

%I A082768 #16 Aug 27 2025 08:45:01
%S A082768 1,3,7,9,10,11,12,13,14,15,16,17,18,19,30,31,32,33,34,35,36,37,38,39,
%T A082768 70,71,72,73,74,75,76,77,78,79,90,91,92,93,94,95,96,97,98,99,100,101,
%U A082768 102,103,104,105,106,107,108,109,110,111,112,113,114,115,116,117,118,119
%N A082768 Numbers that begin with 1, 3, 7 or 9.
%p A082768 isA082768 := proc(n)
%p A082768     convert(n,base,10) ;
%p A082768     if op(-1,%) in {1,3,7,9} then
%p A082768         true;
%p A082768     else
%p A082768         false;
%p A082768     end if;
%p A082768 end proc:
%p A082768 A082768 := proc(n)
%p A082768     if n = 1 then
%p A082768         1;
%p A082768     else
%p A082768         for a from procname(n-1)+ 1 do
%p A082768             if isA082768(a) then
%p A082768                 return a;
%p A082768             end if;
%p A082768         end do:
%p A082768     end if;
%p A082768 end proc:
%p A082768 seq(A082768(n),n=1..120) ; # _R. J. Mathar_, Aug 27 2025
%t A082768 Select[Range[119], MemberQ[{1, 3, 7, 9}, First[IntegerDigits[#]]] &] (* _Jayanta Basu_, Jun 24 2013 *)
%Y A082768 Cf. A082769, A082770, A045572 (Numbers that end with 1, 3, 7 or 9).
%Y A082768 Cf. A082769, A082770, A089743.
%K A082768 base,easy,nonn,changed
%O A082768 1,2
%A A082768 _Amarnath Murthy_, Apr 18 2003
%E A082768 More terms from _David Wasserman_, Jul 28 2005
%E A082768 Offset changed by _Andrew Howroyd_, Sep 29 2024