A175523 a(n)=a(n-1)+ p, where p is the least prime whose first digit equals the first digit of a(n-1) and p>=a(n-1).

1, 12, 25, 54, 113, 226, 453, 910, 1821, 3644, 7303, 14610, 29231, 58462, 116939, 233892, 467803, 935616, 1871237, 3742486, 7484979, 14969998, 29939999, 59880012, 119760031, 239520072, 479040191, 958080388, 1916160779, 3832321566

Offset: 1

Author

Ctibor O. Zizka, Dec 03 2010

Keywords

• nonn
• base
• easy
• less

Examples

			a(0)=1, least prime >=1 with the first digit 1 is 11, so a(1)=1+11=12, least prime >=12 with the first digit 1 is 13, so a(2)=12+13=25, least prime >=25 with the first digit 2 is 29, so a(3)=25+29=54, ...etc.
		

Crossrefs

Cf.A000040

Programs

Maple

A000030 := proc(n) op(-1,convert(n,base,10)) ; end proc:
A175523 := proc(n) option remember; if n = 1 then 1; else a1 := procname(n-1) ; fda := A000030(a1) ; p := nextprime(a1-1) ; while true do if A000030(p) = fda then return p+a1 ; end if; p := nextprime(p) ; end do: end if; end proc:
seq(A175523(n),n=1..30); # R. J. Mathar, Dec 05 2010