Search: id:A108317
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%I A108317
%S A108317 1,1,140,1,0,1,2,0,2,1,0,1,4,0,4,1,0,1,4,0,0,1,0,23,4,0,2,1,0,1,8,0,
%T A108317 4198,497,0,1,2,0,8,1,0,1,0,0,2,1,0,35,2,0,2,1,0,0,2,0,4,1,0,1,2,0,4,17,
%U A108317 0,1,64,0,2,1,0,1,14,0,2,0,0,1
%N A108317 Smallest a(n) such that a(n) n's plus a(n) is prime, or 0 if no such 
               a(n) exists.
%C A108317 Some of the larger entries may only correspond to probable primes.
%C A108317 Some or all of the zero values are merely conjectures. - N. J. A. Sloane 
               (njas(AT)research.att.com).
%C A108317 a(n)=0 for n = 3m+2 (1<=m) (they are all divisible by 3) or n=11m+10 
               (1<=m<9) (they are all divisible by 11) and if a(n) is not 0 then 
               n and a(n) are of opposite parity. - Robert G. Wilson v and Rick 
               L. Shepherd, Jul 28 2005.
%F A108317 a(A016789(n)) = a(A017509(n)) = 0 for n >= 1. a(n) = 1 iff n is a term 
               of A006093. - Rick L. Shepherd (rshepherd2(AT)hotmail.com), Jul 26 
               2005
%e A108317 a(13)=4: 4 13s plus 4 = 13131313+4 = 13131317, which is prime.
%t A108317 f[n_] := If[(n > 4 && Mod[n, 3] == 2) || (n > 20 && Mod[n, 11] == 10), 
               k = 0, If[n == 1, k = 1, Block[{id = IntegerDigits[n]}, k = Mod[n, 
               2] + 1; While[ !PrimeQ[ FromDigits[ Flatten[ Table[id, {k}]]] + k], 
               k += 2]]]; k]; Table[ f[n], {n, 100}] (* only good for n<109 *) (from 
               Robert G. Wilson v (rgwv(AT)rgwv.com), Jun 30 2005)
%o A108317 (PARI) /* for nonzero terms */ a(n) = m=1;pr=n;while(!isprime(pr+m),m++;
               pr=eval(concat(Str(pr),n)));m (Shepherd)
%Y A108317 Cf. A006093 (primes minus 1), A016789 (3n + 2), A017509 (11n + 10).
%Y A108317 Sequence in context: A001163 A140791 A158527 this_sequence A114825 A131492 
               A090945
%Y A108317 Adjacent sequences: A108314 A108315 A108316 this_sequence A108318 A108319 
               A108320
%K A108317 base,nonn
%O A108317 1,3
%A A108317 Ray G. Opao (1260(AT)email.com), Jun 30 2005
%E A108317 a(33) - a(78) from Robert G. Wilson v (rgwv(at)rgwv.com) with guidance 
               from Rick L. Shepherd (rshepherd2(AT)hotmail.com), Jul 28 2005
%E A108317 The sequence continues: 0,4490,1,0,13,14,0,0,1,0,349,10,0,86,2539,0,1,
               4,0,124,1,0,1,4,0,2,1,0,1,2,0,302,1,0,83,2,0,2,5,0,a(120)>5364,2,
               0,278,5,0,...,. - Robert G. Wilson v (rgwv(at)rgwv.com), Jul 28 2005
%E A108317 a(79)>14179 - Robert G. Wilson v (rgwv(at)rgwv.com), Jul 28 2005

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