This site is supported by donations to The OEIS Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A180943 Odd composite numbers m for which 12*|A000367((m+1)/2)|==(-1)^{(m-1)/ 2}* A002445((m+1)/2) (mod m). 1
 33, 169, 481, 561, 793, 805, 949, 1105, 1261, 1417, 1645, 1729, 2041, 2353, 2465, 2509, 2821, 2977, 3133, 3421, 3445, 3601, 4069, 4123, 4381, 4537, 4849, 5161, 5317, 5473, 5629, 5841, 6061, 6205, 6601, 7033, 7093, 7189, 7501, 7813, 7885, 7969, 8113 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS These are pseudoprimes in the sense that the congruence of the definition is valid if any odd prime is substituted for m. Entries of the form m = 4*k+3 are apparently rare: 4123, 8911, ... Computed to 50 terms by D. S. McNeil, Sep 05 2010. LINKS V. Shevelev, B-pseudoprimes, seqfan list, Sep 04 2010 Vladimir Shevelev, The number of permutations with prescribed up-down structure as a function of two variables, INTEGERS, 12 (2012), #A1. [N. J. A. Sloane, Feb 07 2013] MAPLE A000367 := proc(n) numer(bernoulli(2*n)) ; end proc: A002445 := proc(n) denom(bernoulli(2*n)) ; end proc: isA180943 := proc(m) if type(m, 'odd') and not isprime(m) then 12*abs(A000367((m+1)/2)) mod m = (-1)^((m-1)/2)*A002445((m+1)/2) mod m ; else false; end if; end proc: A180943 := proc(n) option remember; if n = 1 then 33; else for a from procname(n-1)+2 by 2 do if isA180943(a) then return a; end if; end do: end if; end proc: # R. J. Mathar, Oct 24 2010 CROSSREFS Cf. A000367, A002445, A180942. Sequence in context: A183776 A256021 A172077 * A113752 A155883 A071914 Adjacent sequences:  A180940 A180941 A180942 * A180944 A180945 A180946 KEYWORD nonn AUTHOR Vladimir Shevelev, Sep 27 2010 EXTENSIONS Comments rephrased and program added by R. J. Mathar, Oct 24 2010 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 April 26 09:52 EDT 2019. Contains 322472 sequences. (Running on oeis4.)