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A114758
Smallest prime of the form: n successive positive integers in descending order followed by a 1.
9
11, 211, 5431, 76541, 17161514131, 1211109871, 98765431, 876543211, 9876543211, 242322212019181716151, 11109876543211, 1131121111101091081071061051041031021, 555453525150494847464544431
OFFSET
1,1
LINKS
EXAMPLE
a(4) = 76541, four successive positive integers 7,6,5,4 in descending order followed by a 1.
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 *)
KEYWORD
base,nonn
AUTHOR
Amarnath Murthy, Jan 01 2006
EXTENSIONS
More terms from Robert G. Wilson v, Jan 03 2006
STATUS
approved