The OEIS is supported by the many generous donors to the OEIS Foundation.

 Year-end appeal: Please make a donation to the OEIS Foundation to support ongoing development and maintenance of the OEIS. We are now in our 60th year, we have over 367,000 sequences, and we’ve reached 11,000 citations (which often say “discovered thanks to the OEIS”). Other ways to Give
 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A330901 Numbers k such that k and k+2 have the same deficiency (A033879). 4
 2, 6497, 12317, 91610, 133787, 181427, 404471, 439097, 485237, 1410119, 2696807, 6220607, 6827369, 6954767, 9770027, 10302419, 10449347, 10887977, 11014007, 16745387, 18959111, 25883519, 27334469, 39508037, 40311149, 40551617, 42561437, 44592209, 47717471, 48912107 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS Are 2 and 91610 the only even terms? Are there any abundant numbers (A005101) in this sequence? Numbers k such that k and k+1 have the same deficiency are 1, 145215, and no more below 10^13 (they are a subset of A112645). Up to a(2214) = 2001876242879 there are no further even terms nor abundant terms. - Giovanni Resta, May 01 2020 LINKS Amiram Eldar, Table of n, a(n) for n = 1..500 EXAMPLE 2 is a term since 2 and 4 have the same deficiency: A033879(2) = 2*2 - sigma(2) = 4 - 3 = 1, and A033879(4) = 2*4 - sigma(4) = 8 - 7 = 1. MATHEMATICA def[n_] := 2*n - DivisorSigma[1, n]; Select[Range[10^5], def[#] == def[# + 2] &] PROG (PARI) j1=1; j2=1; for(k=3, 50000000, j=k+k-sigma(k); if(j==j1, print1(k-2, ", ")); j1=j2; j2=j) \\ Hugo Pfoertner, May 01 2020 CROSSREFS Cf. A000203, A033879, A033880, A112645. Sequence in context: A349512 A107021 A107022 * A285693 A112720 A129059 Adjacent sequences: A330898 A330899 A330900 * A330902 A330903 A330904 KEYWORD nonn AUTHOR Amiram Eldar, May 01 2020 STATUS approved

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

Last modified December 9 23:44 EST 2023. Contains 367696 sequences. (Running on oeis4.)