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A332454
Starting from sigma(n)+1, number of halving steps to reach 1 in '3x+1' problem, or -1 if this never happens.
4
1, 2, 4, 3, 11, 7, 13, 4, 12, 14, 7, 13, 12, 16, 16, 5, 14, 7, 6, 20, 18, 15, 16, 14, 5, 20, 69, 22, 67, 73, 18, 6, 17, 71, 17, 13, 23, 14, 22, 59, 20, 75, 12, 8, 24, 73, 17, 69, 14, 67, 73, 18, 71, 61, 73, 61, 16, 59, 14, 33, 68, 75, 26, 7, 8, 74, 11, 31, 75, 74, 73, 19, 11, 23, 69, 12, 75, 33, 16, 30, 15, 31, 8, 35, 72, 20
OFFSET
1,2
FORMULA
a(n) = A006666(A088580(n)) = A006666(1+sigma(n)).
PROG
(PARI)
A006666(n) = { my(t=0); while(n>1, if(n%2, n=3*n+1, n>>=1; t++)); (t); }; \\ From A006666
A332454(n) = A006666(1+sigma(n));
CROSSREFS
KEYWORD
nonn
AUTHOR
Antti Karttunen, Feb 16 2020
STATUS
approved