A336122 Numbers k for which A335884(k) = 2.

5, 7, 9, 10, 14, 18, 20, 28, 36, 40, 56, 72, 80, 112, 144, 160, 224, 288, 320, 448, 576, 640, 896, 1152, 1280, 1792, 2304, 2560, 3584, 4608, 5120, 7168, 9216, 10240, 14336, 18432, 20480, 28672, 36864, 40960, 57344, 73728, 81920, 114688, 147456, 163840, 229376, 294912, 327680, 458752, 589824, 655360, 917504, 1179648, 1310720

Offset

1,1

Comments

Numbers n such that when we start from k = n, and apply in any combination the nondeterministic maps k -> k - k/p and k -> k + k/p, (where p can be any of the odd prime factors of k), a power of 2 will appear no later than after two such steps, and on some of the combinations a power of 2 will appear after exactly two steps.

Links

Table of n, a(n) for n=1..55.

Prog

(PARI)
A335884(n) = { my(f=factor(n)); sum(k=1, #f~, if(2==f[k, 1], 0, f[k, 2]*(1+max(A335884(f[k, 1]-1), A335884(f[k, 1]+1))))); };
isA336122(n) = (2==A335884(n));

Crossrefs

Cf. A335884.

Cf. also A334102, A335882, A335912.

Sequence in context: A189703 A158251 A212191 * A241853 A165513 A002342

Adjacent sequences: A336119 A336120 A336121 * A336123 A336124 A336125

Keyword

nonn

Author

Antti Karttunen, Jul 09 2020

Status

approved