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a(n+1) = a(n)-th composite and a(1) = 13.
3

%I #7 May 14 2018 18:28:35

%S 13,22,34,50,70,95,126,165,213,272,341,424,524,640,778,938,1127,1345,

%T 1596,1886,2217,2596,3031,3523,4086,4724,5445,6259,7176,8205,9364,

%U 10666,12118,13744,15560,17583,19827,22328,25099,28171,31569,35334

%N a(n+1) = a(n)-th composite and a(1) = 13.

%H Chai Wah Wu, <a href="/A059408/b059408.txt">Table of n, a(n) for n = 1..900</a>

%t g[ n_Integer ] := (k = n + PrimePi[ n ] + 1; While[ k - PrimePi[ k ] - 1, k++ ]; k); NestList[ g, 13, 45 ]

%o (PARI) lista(nn) = {print1(a = 13, ", "); nb = 0; forcomposite(c=1, nn, nb++; if (nb==a, print1(c, ", "); a = c););} \\ _Michel Marcus_, May 14 2018

%Y Cf. A006508, A059407.

%K nonn

%O 1,1

%A _Robert G. Wilson v_, Jan 29 2001