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A221980 Number of primes of the form (x+1)^7 - x^7 with x <= 10^n. 1
1, 6, 24, 161, 1094, 8283, 66790 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

COMMENTS

Number of primes equal to the difference of two consecutive seventh powers (x+1)^7 - x^7 = 7x(x+1)(x^2+x+1)^2+1  (A121618). Values of x = A121619 - 1.  Sequence of number of primes of the form (x+1)^7 - x^7 with x <= 10^n have similar characteristics to similar sequences for natural primes, cuban primes (A221794) and primes of the form (x+1)^5 - x^5 (A221849).

LINKS

Table of n, a(n) for n=0..6.

MATHEMATICA

Table[Count[#[[2]]-#[[1]]&/@Partition[Range[10^n+1]^7, 2, 1], _?PrimeQ], {n, 0, 6}] (* Harvey P. Dale, Sep 17 2019 *)

PROG

(PARI) a(n) = {nb = 0; for (i = 1, 10^n, if (isprime((i+1)^7-i^7), nb++); ); nb; } \\ Michel Marcus, Sep 18 2013

CROSSREFS

Sequence in context: A165638 A122829 A232688 * A225827 A200904 A293488

Adjacent sequences:  A221977 A221978 A221979 * A221981 A221982 A221983

KEYWORD

nonn,base

AUTHOR

Vladimir Pletser, Feb 02 2013

STATUS

approved

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Last modified October 18 05:45 EDT 2019. Contains 328146 sequences. (Running on oeis4.)