login
A085344
Least number x such that number of primes between sigma(x) and x equals n.
1
2, 4, 10, 12, 16, 46, 28, 24, 44, 30, 42, 40, 36, 54, 48, 66, 178, 78, 104, 80, 102, 60, 128, 72, 84, 152, 90, 138, 255, 96, 108, 174, 140, 126, 132, 266, 160, 150, 248, 222, 156, 120, 246, 200, 144, 198, 634, 224, 220, 204, 370, 260, 168, 376, 555, 430, 354, 308
OFFSET
1,1
LINKS
FORMULA
a(n) = Min{x; A085341(x)=n}.
MATHEMATICA
m = 100; seq = Table[0, {m}]; c = 0; n = 0; While[c < m, n++; i = PrimePi[ DivisorSigma[1, n]] - PrimePi[n]; If[i <= m && seq[[i]] == 0, c++; seq[[i]] = n]]; seq (* Amiram Eldar, Mar 01 2020 *)
PROG
(PARI) a(n) = {my(x=1); while (primepi(sigma(x)) - primepi(x) != n, x++); x; } \\ Michel Marcus, Mar 01 2020
KEYWORD
nonn
AUTHOR
Labos Elemer, Jul 10 2003
STATUS
approved