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A076623
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Total number of left truncatable primes (without zeros) in base n.
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11
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0, 3, 16, 15, 454, 22, 446, 108, 4260, 75, 170053, 100, 34393, 9357, 27982, 362, 14979714, 685, 3062899, 59131, 1599447, 1372, 1052029701, 10484, 7028048, 98336, 69058060, 3926
(list; graph; refs; listen; history; internal format)
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OFFSET
| 2,2
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COMMENTS
| Approximation of a(b) by (PARI) code: l(b)=c=b*(b-1)/log(b)/eulerphi(b);\ return(floor((primepi(b)-omega(b))*exp(c)/c));
a(24)=1052029701 based on strong BPSW pseudoprimes. Other terms up to a(29) use proved primes. [From Martin Fuller (martin_n_fuller(AT)btinternet.com), Nov 24 2008]
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LINKS
| Angell, I. O. and Godwin, H. J., On Truncatable Primes, Math. Comput. 31, 265-267, 1977.
Martin Fuller, Table of n, a(n) for n= 2..53, with question marks where unknown
Hans Havermann, A076623 Decomposed
Index entries for sequences related to truncatable primes
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MAPLE
| Lton := proc(L, b) add( op(i, L)*b^(i-1), i=1..nops(L)) ; end proc:
A076623rec := proc(L, b) local a, d, Lext, p ; a := 0 ; for d from 1 to b-1 do Lext := [op(L), d] ; p := Lton(Lext, b) ; if isprime(p) then a := a+1 ; a := a+procname(Lext, b) ; end if; end do: a ; end proc:
A076623 := proc(b) A076623rec([], b) ; end proc:
for b from 2 do print(b, A076623(b)) ; end do: # R. J. Mathar, Jun 01 2011
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PROG
| (PARI code from Robert Gerbicz (robert.gerbicz(AT)gmail.com), Oct 31 2008)
f(b)=ct=0; A=[0]; n=-1; L=1; while(L, n++; B=vector(L*b); M=0; \
for(i=1, L, for(j=1, b-1, x=A[i]+j*b^n; if(isprime[x], M++; B[M]=x; ct++))); \
L=M; A=vector(L, i, B[i])); return(ct)
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CROSSREFS
| Cf. A024779, A024780, A024781, A024782, A024783, A024784, A024785, A076586.
Cf. A103443, A103463.
Sequence in context: A063709 A195880 A195883 * A068516 A032922 A103655
Adjacent sequences: A076620 A076621 A076622 * A076624 A076625 A076626
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KEYWORD
| nonn
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AUTHOR
| Martin Renner (martin.renner(AT)gmx.net), Oct 22 2002, Nov 03 2002, Sep 24 2007, Feb 20 2008, Apr 20 2008
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EXTENSIONS
| a(12) corrected from 170051 to 170053 by Martin Fuller (martin_n_fuller(AT)btinternet.com), Oct 31 2008
Correction of a(18) and approximation for a(n). - Robert Gerbicz (robert.gerbicz(AT)gmail.com), Nov 02 2008
a(24) - a(29) from Martin Fuller (martin_n_fuller(AT)btinternet.com), Nov 24 2008
Entries in a-file corrected by N. J. A. Sloane, Jun 02 2011
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