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A077275 Least number which can be represented by the difference between two successive powers of a prime but not a prime (A077273) in just n ways. 0
1, 4, 17, 801528, 187117320, 17036037480 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

Table of n, a(n) for n=1..6.

EXAMPLE

1 = 9-8, 4 = 8-4 & 125-121, 17 = 49 - 32 = 81 -64 = 529 - 512, 801528 = 1115760409 - 1114958881 = 4461839209 - 4461037681 = 10038637249 - 10037835721 = 40153346689 - 40152545161 and

187117320 = 9725896737769 - 9725709620449 = 21883150711249 - 21882963593929 = 60786363426721 - 60786176309401 = 243145173030769 - 243144985913449 = 2188305808807561 - 2188305621690241.

MATHEMATICA

pp = Sort[ Flatten[ Table[ Prime[n]^i, {n, 1, PrimePi[ Sqrt[10^16]]}, {i, 1, Log[ Prime[n], 10^16]}]]]; l = Length[pp]; b = Sort[ Take[pp, -l + 1] - Take[pp, l - 1]];

CROSSREFS

Cf. A025475.

Sequence in context: A041701 A154131 A132554 * A059903 A227540 A246133

Adjacent sequences:  A077272 A077273 A077274 * A077276 A077277 A077278

KEYWORD

more,nonn

AUTHOR

Robert G. Wilson v, Oct 31 2002

EXTENSIONS

a(6) from Donovan Johnson, Jun 19 2008

STATUS

approved

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Last modified May 25 10:01 EDT 2020. Contains 334592 sequences. (Running on oeis4.)