A114758 Smallest prime of the form: n successive positive integers in descending order followed by a 1.
11, 211, 5431, 76541, 17161514131, 1211109871, 98765431, 876543211, 9876543211, 242322212019181716151, 11109876543211, 1131121111101091081071061051041031021, 555453525150494847464544431
Offset: 1
Examples
a(4) = 76541, four successive positive integers 7,6,5,4 in descending order followed by a 1.
Links
- Robert Israel, Table of n, a(n) for n = 1..173
Programs
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Maple
f:= proc(n) local k,p,j; for k from 0 do p:= parse(cat(seq(k+j,j=n .. 1,-1), 1)); if isprime(p) then return p fi od end proc:map(f, [$1..15]); # Robert Israel, Apr 03 2023 -
Mathematica
a[n_]:=(For[m=1, (v={};Do[v=Join[v, IntegerDigits[k]], {k, m+n-1, m, -1}]);!PrimeQ[10FromDigits[v]+1], m++ ];10FromDigits[v]+1);Table[a[n], {n, 14}] (* Farideh Firoozbakht, Jan 02 2006 *) f[n_] := Block[{t = Reverse@Range@n}, While[p = FromDigits@Flatten@IntegerDigits@Join[t, {1}]; ! PrimeQ@p, t++ ]; p]; Array[f, 13] (* Robert G. Wilson v, Jan 03 2006 *)
Extensions
More terms from Robert G. Wilson v, Jan 03 2006