Logo

Greetings from The On-Line Encyclopedia of Integer Sequences!

Hints

Search: id:A057838
Displaying 1-1 of 1 results found. page 1
     Format: long | short | internal | text      Sort: relevance | references | number      Highlight: on | off
A057838 Indices n in A055079 corresponding to "difficult" cases: A001221[A055079(n)]=1. The corresponding smallest numbers which have n composite divisors = 2^n. +0
3
1, 3, 11, 35, 71, 191, 419, 659, 1091, 1199, 1379, 1655, 2015, 2135, 2339, 2591, 3059, 4439, 6119, 6215, 6335, 7055, 8099, 8351, 8519, 9815, 12419, 12431, 12599, 12719, 12851, 13679, 15119, 15239 (list; graph; listen)
OFFSET

0,2

EXAMPLE

11 is here: 2^11 has 11 nonprime divisors; c(11)=A055079(11) could not have r=2, 3, 4 or more distinct prime divisors because 11+{2, 3, 4, 5, 6, 7, 8, 9, ...} values of corresponding d[c(11)]={13, 14, 15, ..} had 1, 2, 2, 4, 1, 3, 1, 3, 2, 2, 1, 4, 2, 2 non-distinct prime divisors which provides upper bound for r... in contradiction with demanded values: 2, 3, 4, 5, 6, 7, ... This is why A055079(11)=2048. Larger cases are handled in a similar way.

The largest known value of A055079 is A055079(15239)=2^15239 which has 4588 decimal digits.

A protocol for 15239 is as follows: u=15239; t0=Table[s, {s, 0, 17}]; t1=Table[mr[w], {w, u, u+17}]; t2=t1-t0; g=Table[{w, mr[w]}, {w, u, u+17}]; i1=TimeUsed[]; Write["a(bad)tx1", u, t1, t2, g]; 15239

Supposed number of A001221(x) which should be larger or equal than A001222[d(x)]: {0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17}

A001222[d(x)] {3, 6, 1, 2, 2, 4, 2, 6, 2, 5, 4, 5, 2, 5, 2, 3, 5, 4}

A001222[d(x)] - A001221(x) (negative value means "nasty case") {3, 5, -1, -1, -2, -1, -4, -1, -6, -4, -6, -6, -10, -8, -12, -12, -11, -13} numbers (corresponding d(x) values for some x) together with A001222[d(x)] {{15239, 3}, {15240, 6}, {15241, 1}, {15242, 2}, {15243, 2}, {15244, 4}, {15245, 2}, {15246, 6}, {15247, 2}, {15248, 5}, {15249, 4}, {15250, 5}, {15251, 2}, {15252, 5}, {15253, 2}, {15254, 3}, {15255, 5}, {15256, 4}}

CROSSREFS

Cf. A055079, A001221, A001222, A000005, A058060, A058061, A057841.

Sequence in context: A037496 A134326 A094308 this_sequence A088578 A027060 A126939

Adjacent sequences: A057835 A057836 A057837 this_sequence A057839 A057840 A057841

KEYWORD

nonn

AUTHOR

Labos E. (labos(AT)ana.sote.hu), Nov 24 2000

page 1

Search completed in 0.002 seconds

Lookup | Welcome | Find friends | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Transforms | Puzzles | Hot | Classics
More pages | Superseeker | Maintained by N. J. A. Sloane (njas@research.att.com)

Last modified July 25 07:41 EDT 2008. Contains 142293 sequences.


AT&T Labs Research