A379003 Ordinal transform of A132741, where A132741 is the largest divisor of n having the form 2^i*5^j. a(0) = 0 by convention.

0, 1, 1, 2, 1, 1, 2, 3, 1, 4, 1, 5, 2, 6, 3, 2, 1, 7, 4, 8, 1, 9, 5, 10, 2, 1, 6, 11, 3, 12, 2, 13, 1, 14, 7, 3, 4, 15, 8, 16, 1, 17, 9, 18, 5, 4, 10, 19, 2, 20, 1, 21, 6, 22, 11, 5, 3, 23, 12, 24, 2, 25, 13, 26, 1, 6, 14, 27, 7, 28, 3, 29, 4, 30, 15, 2, 8, 31, 16, 32, 1, 33, 17, 34, 9, 7, 18, 35, 5, 36, 4, 37, 10

Offset: 0

Author

Antti Karttunen, Dec 15 2024

Keywords

• nonn

Comments

Ordinal transform of the ordered pair [A007814(n), A112765(n)].

This sequence and A379004 are ordinal transforms of each other (if the initial 0 is discarded).

Links

• Antti Karttunen, Table of n, a(n) for n = 0..20000

Crossrefs

Cf. A007814, A112765, A132741, A379004 (ordinal transform of this sequence after the initial 0).

Cf. also A126760, A379006.

Programs

PARI

up_to = 20000;
ordinal_transform(invec) = { my(om = Map(), outvec = vector(length(invec)), pt); for(i=1, length(invec), if(mapisdefined(om,invec[i]), pt = mapget(om, invec[i]), pt = 0); outvec[i] = (1+pt); mapput(om,invec[i],(1+pt))); outvec; };
v379003 = ordinal_transform(vector(up_to, n, [valuation(n,2), valuation(n,5)]));
A379003(n) = if(!n,n,v379003[n]);