Try this PARI/GP program for the length of Aliquot sequence!!!

sweety439 · 2022-07-14, 09:28

Code:

a(n)=if(n==0 || sigma(n)==2*n,0,a(sigma(n)-n)+1)

enter a(138), it can print 178 (which is the length of Aliquot sequence of 138) in < 1 second.

you can try a(276), but .... Warning!!! Please do not try a(220)

sweety439 · 2022-07-18, 16:52

This PARI/GP program can print terms of https://oeis.org/A115350, and thus we may not write its b-file by hand:

Code:

a(n)=if(isprime(n) || sigma(n)==2*n || n==220 || n==1184 || n==2620 || n==5020 || n==6232 || n==10744 || n==12285 || n==17296 || n==63020 || n==66928 || n==67095 || n==69615 || n==79750 || n==12496 || n==14316, n, if(n>10^70, 0, a(sigma(n)-n)))

(given by terms of https://oeis.org/A002025 and https://oeis.org/A003416, this program is sufficient up to n=10^5)

2022-07-14, 09:28	#1
sweety439 "99(4^34019)99 palind" Nov 2016 (P^81993)SZ base 36 2⁵·5·23 Posts	Try this PARI/GP program for the length of Aliquot sequence!!! Code: a(n)=if(n==0 \|\| sigma(n)==2n,0,a(sigma(n)-n)+1) enter a(138), it can print 178 (which is the length of Aliquot sequence of 138) in < 1 second. you can try a(276), but .... Warning!!! Please do not try a(220)* Last fiddled with by sweety439 on 2022-07-14 at 09:32

2022-07-18, 16:52	#2
sweety439 "99(4^34019)99 palind" Nov 2016 (P^81993)SZ base 36 2⁵×5×23 Posts	This PARI/GP program can print terms of https://oeis.org/A115350, and thus we may not write its b-file by hand: Code: a(n)=if(isprime(n) \|\| sigma(n)==2n \|\| n==220 \|\| n==1184 \|\| n==2620 \|\| n==5020 \|\| n==6232 \|\| n==10744 \|\| n==12285 \|\| n==17296 \|\| n==63020 \|\| n==66928 \|\| n==67095 \|\| n==69615 \|\| n==79750 \|\| n==12496 \|\| n==14316, n, if(n>10^70, 0, a(sigma(n)-n))) (given by terms of https://oeis.org/A002025 and https://oeis.org/A003416, this program is sufficient up to n=10^5) Last fiddled with by sweety439 on 2022-07-18 at 16:56*

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