OFFSET
0,3
COMMENTS
Conjecture: no entry is zero for n>2.
Conjecture: each term after the first two terms ends with 7. - Harvey P. Dale, May 26 2018
LINKS
Harvey P. Dale, Table of n, a(n) for n = 0..100
MATHEMATICA
LastDigit[n_] := n - 10*Floor[n/10]; FirstDigit[n_] := Floor[n/(10^(Ceiling[Log[10, n]] - 1))]; MiddleDigits[n_] := Floor[(n - Floor[n/(10^(Ceiling[Log[10, n]] - 1))]*10^(Ceiling[Log[10, n]] - 1))/10]; IntExtPrimeTest2[n_] := TrueQ[(Boole[PrimeQ[FirstDigit[n]*10 + LastDigit[ n]]] + Boole[PrimeQ[MiddleDigits[n]]] + Boole[PrimeQ[n]]) == 3]; finder[digits_] := (maxj = 10^digits; For[j = maxj, IntExtPrimeTest2[j] == False, j-- ]; Print[j]); Do[finder[n], {n, 3, 25}] - Joshua Albert (jba138(AT)psu.edu), Feb 22 2006
eidQ[n_]:=Module[{idn=IntegerDigits[n]}, AllTrue[{FromDigits[Join[ {idn[[1]]}, {idn[[-1]]}]], FromDigits[Most[Rest[idn]]]}, PrimeQ]]; Join[ {0, 0}, Table[Module[{np=NextPrime[10^n-1, -1]}, While[ !eidQ[np], np = NextPrime[ np, -1]]; np], {n, 3, 18}]] (* The program uses the AllTrue function from Mathematica version 10 *) (* Harvey P. Dale, May 26 2018 *)
CROSSREFS
KEYWORD
base,nonn
AUTHOR
Amarnath Murthy, Nov 05 2002
EXTENSIONS
Corrected and extended by Joshua Albert (jba138(AT)psu.edu), Feb 22 2006
STATUS
approved