A267237 - OEIS

A267237

Numbers n such that 'n-1' prepended to 'n' n times yield primes.

7, 19, 989, 1187, 4183

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OFFSET

1,1

COMMENTS

a(5) produces the prime: 4182...[4183 times]4183 (16736 digits).

LINKS

EXAMPLE

7 occurs because '6' prepended 7 times to '7' produces prime (66666667).

MATHEMATICA

Select[ Range[1200], PrimeQ[ FromDigits[ StringJoin@@ ToString/@ PadLeft[{#}, #+1, #-1]]] &]

CROSSREFS

KEYWORD

nonn,more,hard

AUTHOR

STATUS

approved