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A256520 Number of primes between the n-th and (n+1)-st Carmichael numbers. 1
83, 84, 95, 46, 443, 255, 182, 557, 1341, 1107, 526, 553, 923, 114, 1014, 2255, 1278, 880, 3039, 796, 1364, 5212, 2070, 1252, 1614, 1544, 496, 4554, 837, 3013, 3051, 1788, 1430, 1628, 7786, 160, 839, 5825, 5682, 941, 1066, 10506, 1977, 655, 1232, 2288, 4989 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Amiram Eldar, Table of n, a(n) for n = 1..5000

MATHEMATICA

lst = Cases[Range[1, 100000, 2], n_ /; Mod[n, CarmichaelLambda@ n] == 1 && ! PrimeQ@ n]; Reap@ For[k = 1, k < Length@ lst, k++, Sow@ Count[Range[lst[[k]], lst[[k + 1]]], _?PrimeQ]] // Flatten // Rest (* Michael De Vlieger, Apr 03 2015, after Artur Jasinski at A002997 *)

PROG

(PARI) vi=readvec("b002997.txt")

a(n)=primepi(vi[n+1])-primepi(vi[n])

CROSSREFS

Cf. A002997.

Sequence in context: A106418 A031961 A108751 * A307733 A130286 A226380

Adjacent sequences:  A256517 A256518 A256519 * A256521 A256522 A256523

KEYWORD

nonn

AUTHOR

Felix Fröhlich, Apr 01 2015

STATUS

approved

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Last modified April 8 04:26 EDT 2020. Contains 333312 sequences. (Running on oeis4.)