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A139435 Largest m<n such that first terms of the Collatz trajectory of m sum up to n; a(n)=0 if no such m exists. 2
0, 0, 2, 0, 1, 4, 4, 1, 6, 2, 4, 8, 4, 8, 10, 2, 2, 12, 8, 4, 14, 8, 2, 16, 4, 8, 18, 16, 8, 20, 16, 4, 22, 4, 20, 24, 16, 16, 26, 8, 4, 28, 14, 16, 30, 10, 8, 32, 28, 10, 34, 16, 13, 36, 24, 32, 38, 16, 20, 40, 15, 32, 42, 12, 20, 44, 32, 8, 46, 40, 28, 48, 20, 32, 50, 32, 44, 52, 26, 20 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,3

COMMENTS

a(n) = 0 iff A139436(n) = 0; a(n) > 0 for n > 4;

a(n) <= A004523(n); a(A008585(n)) = A005843(n).

LINKS

R. Zumkeller, Table of n, a(n) for n = 1..10000

Eric Weisstein's World of Mathematics, Collatz Problem

Index entries for sequences related to 3x+1 (or Collatz) problem

EXAMPLE

a(30) = 20: 30 = 20+10;

a(31) = 16: 31 = 16+8+4+2+1;

a(32) = 4: 32 = 4+2+1+4+2+1+4+2+1+4+2+1+4;

a(33) = 22: 33 = 22+11;

a(34) = 4: 34 = 4+2+1+4+2+1+4+2+1+4+2+1+4+2;

a(35) = 20: 35 = 20+10+5.

CROSSREFS

Cf. A006370.

Sequence in context: A264583 A158984 A158417 * A077909 A247126 A327117

Adjacent sequences:  A139432 A139433 A139434 * A139436 A139437 A139438

KEYWORD

nonn

AUTHOR

Reinhard Zumkeller, Apr 21 2008

STATUS

approved

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Last modified January 27 17:58 EST 2020. Contains 331296 sequences. (Running on oeis4.)