The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A275370 Odd numbers n such that sigma(n) = sigma(2*n-1). 2
 1, 13545, 57645, 116865, 1440495, 7029855, 8596455, 27361125, 41100345, 48289185, 56122185, 77560065, 103225185, 134813385, 146591235, 163817745, 188358885, 198748305, 242668335, 269436375, 352094715, 358841385, 535135965, 563911335, 636719265, 712457655, 724692045 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS The smallest term that is not divisible by 5 is 1577106531. LINKS Giovanni Resta, Table of n, a(n) for n = 1..164 (terms < 2*10^11) EXAMPLE The numbers n that solve sigma(n) = sigma(2n-1) are n = 1, 6, 348, 496, 1420, 1854, 4647, 5352, 6424, 13545, 21126,... The sequence selects the odd members. PROG (PARI) isok(n) = sigma(n) == sigma(2*n-1) && n % 2 == 1 CROSSREFS Cf. A000203, A008438, A272553. Sequence in context: A254738 A342858 A064981 * A204785 A249526 A108418 Adjacent sequences:  A275367 A275368 A275369 * A275371 A275372 A275373 KEYWORD nonn AUTHOR Altug Alkan, Jul 25 2016 STATUS approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

Last modified June 21 06:07 EDT 2021. Contains 345357 sequences. (Running on oeis4.)