A079834 - OEIS

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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, 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

(list; graph; refs; listen; history; text; internal format)

OFFSET

1,2

LINKS

Table of n, a(n) for n=1..91.

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

Adjacent sequences: A079831 A079832 A079833 * A079835 A079836 A079837

KEYWORD

nonn

AUTHOR

Amarnath Murthy, Feb 12 2003

EXTENSIONS

More terms from Max Alekseyev, Apr 19 2005

STATUS

approved