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A046273 Largest prime substring in 7^n (0 if none). 3
0, 7, 0, 43, 401, 7, 7649, 823, 4801, 3607, 82475249, 7326743, 41287201, 89, 23072849, 7561, 232930569601, 2630513987207, 8413597910449, 398895185373143, 297612001, 558545864083, 2988049, 3400809163 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

LINKS

Vincenzo Librandi, Table of n, a(n) for n = 0..200

MATHEMATICA

lpss[n_]:=Module[{idn7=IntegerDigits[7^n]}, Max[Select[Flatten[ Table[ FromDigits/@ Partition[idn7, i, 1], {i, Length[idn7]}]], PrimeQ]]]; Array[ lpss, 25, 0]/.-\[Infinity]->0 (* Harvey P. Dale, Aug 17 2013 *)

CROSSREFS

Cf. A046265.

Sequence in context: A157779 A222322 A228762 * A167317 A266436 A240822

Adjacent sequences:  A046270 A046271 A046272 * A046274 A046275 A046276

KEYWORD

nonn

AUTHOR

Patrick De Geest, Jun 15 1998

STATUS

approved

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Last modified December 7 20:25 EST 2019. Contains 329848 sequences. (Running on oeis4.)