A180600 a(n+1) = a(n) if A180458(n+1) = A180458(n), otherwise a(n+1) = a(n)+1.
1, 2, 3, 4, 5, 5, 5, 5, 6, 6, 6, 7, 7, 7, 8, 8, 9, 9, 10, 10, 10, 11, 11, 12, 12, 13, 13, 13, 13, 14, 15, 16, 16, 16, 17, 18, 18, 19, 19, 20, 20, 21, 22, 22, 22, 22, 23, 24, 24, 24, 25, 25, 25, 26, 27, 28, 28, 28, 29, 29, 30, 31, 32, 32, 33, 33, 34, 35, 36, 36, 37, 37, 38, 39, 39, 40, 40, 41
Offset: 1
Links
- Harvey P. Dale, Table of n, a(n) for n = 1..1000
Programs
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Maple
isA002113 := proc(n) n = digrev(n) ; end proc: A180458 := proc(n) local p ; p := ithprime(n) ; while not isA002113(p) do p := p-1 ; end do; p ; end proc: A180600 := proc(n) option remember; if n = 1 then 1; else if A180458(n) = A180458(n-1) then procname(n-1) ; else procname(n-1)+1 ; end if; end if; end proc: seq(A180600(n),n=1..90) ; # R. J. Mathar, Oct 24 2010
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Mathematica
lpn[n_]:=Module[{k=0},While[!PalindromeQ[n-k],k++];n-k]; nxt[{n_,l_,a_}] := Module[{x=lpn[Prime[n+1]]},{n+1,x,If[x==l,a,a+1]}]; NestList[ nxt,{1,1,1},80][[All,3]] (* Requires Mathematica version 10 or later *) (* Harvey P. Dale, Dec 18 2020 *)
Formula
Extensions
Sequence corrected starting near a(54), definition corrected, comment and formula added by R. J. Mathar, Oct 24 2010
Comments