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A285102 a(n) = A007913(A285101(n)). 6
2, 6, 210, 72930, 620310, 278995269860970, 12849025509071310, 492608110538467706074890, 1342951001046021018427857601026746070, 37793589449865555275592120894959094883390892772270, 728982633030274864467458719371654181886452163442582606072870, 28339554655955912942523491885490197708224606885407444005070 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,1

LINKS

Table of n, a(n) for n=0..11.

FORMULA

a(0) = 2, for n > 0, a(n) = lcm(a(n-1),A242378(n,a(n-1))) / gcd(a(n-1),A242378(n,a(n-1))).

a(n) = A007913(A285101(n)).

Other identities. For all n >= 0:

A001221(a(n)) = A001222(a(n)) = A285103(n).

A048675(a(n)) = A068052(n).

PROG

(PARI)

A003961(n) = { my(f = factor(n)); for (i=1, #f~, f[i, 1] = nextprime(f[i, 1]+1)); factorback(f); };

A242378(k, n) = { while(k>0, n = A003961(n); k = k-1); n; };

A285102(n) = { if(0==n, 2, lcm(A285102(n-1), A242378(n, A285102(n-1)))/gcd(A285102(n-1), A242378(n, A285102(n-1)))); };

(Scheme) (definec (A285102 n) (if (zero? n) 2 (/ (lcm (A285102 (- n 1)) (A242378bi n (A285102 (- n 1)))) (gcd (A285102 (- n 1)) (A242378bi n (A285102 (- n 1)))))))

(Python)

from sympy import factorint, prime, primepi

from sympy.ntheory.factor_ import core

from operator import mul

def a003961(n):

    f=factorint(n)

    return 1 if n==1 else reduce(mul, [prime(primepi(i) + 1)**f[i] for i in f])

def a242378(k, n):

    while k>0:

        n=a003961(n)

        k-=1

    return n

l=[2]

for n in xrange(1, 12):

    x=l[n - 1]

    l+=[x*a242378(n, x), ]

print map(core, l) # Indranil Ghosh, Jun 27 2017

CROSSREFS

Cf. A003961, A007913, A048675, A068052, A242378, A285101, A285103.

Sequence in context: A302344 A156517 A091439 * A285101 A176782 A013083

Adjacent sequences:  A285099 A285100 A285101 * A285103 A285104 A285105

KEYWORD

nonn

AUTHOR

Antti Karttunen, Apr 15 2017

STATUS

approved

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Last modified June 25 09:48 EDT 2019. Contains 324347 sequences. (Running on oeis4.)