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A079834
Define f(n)= n + tau(n), then a(n) = k where k is the number of steps required to get the smallest prime of the form f(f(f...f(n)))).
1
1, 2, 1, 1, 1, 11, 11, 10, 10, 10, 1, 9, 2, 9, 1, 10, 1, 8, 10, 8, 9, 8, 9, 7, 8, 7, 1, 7, 1, 6, 2, 6, 1, 6, 2, 4, 2, 5, 1, 95, 1, 4, 4, 4, 3, 4, 96, 94, 95, 3, 2, 94, 2, 93, 1, 2, 1, 93, 1, 9, 3, 92, 2, 1, 2, 91, 2, 91, 1, 90, 1, 8, 91, 90, 90, 90, 90, 89, 90, 88, 89, 89, 2, 7, 1, 88, 5, 7, 5, 87, 4
OFFSET
1,2
EXAMPLE
a(6) = 11 as f(6) = 10, f(10) = 14, f(14) = 18, f(18) = 24, f(24) = 32, f(32) = 38, f(38) = 42, f(42) = 50, f(50) = 56, f(56) = 64, f(64) = 64 +7 = 71.
PROG
(PARI) { a(n) = local(k, m); k=1; m=n; while(1, m=m+numdiv(m); if(isprime(m), return(k)); k++ ) } (Alekseyev)
CROSSREFS
Cf. A079833.
Sequence in context: A105688 A066017 A236938 * A368811 A342458 A358722
KEYWORD
nonn
AUTHOR
Amarnath Murthy, Feb 12 2003
EXTENSIONS
More terms from Max Alekseyev, Apr 19 2005
STATUS
approved