A256520 Number of primes between the n-th and (n+1)-st Carmichael numbers.

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

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 * A130286 A372042 A226380

Adjacent sequences: A256517 A256518 A256519 * A256521 A256522 A256523

Keyword

nonn

Author

Felix Fröhlich, Apr 01 2015

Status

approved