A154522 Numbers n such that number of occurrences of the smallest digit in prime(n) is 2.

5, 30, 32, 36, 42, 43, 47, 48, 49, 50, 64, 68, 71, 74, 76, 84, 87, 102, 130, 138, 139, 141, 151, 156, 165, 169, 188, 189, 191, 192, 195, 196, 198, 199, 202, 210, 215, 216, 218, 221, 230, 233, 234, 242, 248, 255, 256, 257, 268, 271, 282, 284, 286, 293, 294, 297

Offset: 1

Author

Juri-Stepan Gerasimov, Jan 11 2009

Keywords

• nonn
• base

Comments

Indices n such that the smallest digit in prime(n), A060420(n), appears twice in the decimal representation of prime(n). [R. J. Mathar, Jan 12 2009]

Examples

			If 191=prime(n=43), 1=1 and 1<9, the 43=a(6);
If 199=prime(n=45), then 9=9 and 9>1;
If 211=prime(n=47), 1=1 and 1<2, then 47=a(7);
If 223=prime(n=48), 2=2 and 2<3, then 48=a(48), etc.
		

Links

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

Crossrefs

Cf. A000040.

Programs

Maple

A060420 := proc(n) convert(ithprime(n),base,10) ; min(op(%)) ; end: dcount := proc(di,n) local a,d; a := 0 ; convert(n,base,10) ; for d in % do if d = di then a := a+1 ; fi; od; a ; end: isA154522 := proc(n) local d,c ; d := A060420(n) ; c := dcount(d,ithprime(n)) ; RETURN( c = 2 ) ; end: for n from 1 to 800 do if isA154522(n) then printf("%d,",n) ; fi; od: # R. J. Mathar, Jan 12 2009

Mathematica

Select[Range[300],Length[Split[Sort[IntegerDigits[Prime[#]]]][[1]]] == 2&] (* Harvey P. Dale, Aug 16 2011 *)

Extensions

Removed 205, 206, 208. Added 210. R. J. Mathar, Jan 12 2009