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A341779 Numbers k such that k and k+1 are both anti-tau numbers (A046642). 2
3, 4, 15, 16, 64, 100, 195, 196, 255, 256, 483, 484, 676, 783, 784, 1023, 1024, 1155, 1156, 1295, 1296, 1443, 1444, 1599, 1600, 1936, 2116, 2703, 2704, 3363, 3364, 3844, 4096, 4623, 4624, 4899, 4900, 5183, 5184, 5476, 5776, 6399, 6400, 6723, 6724, 7395, 7396 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,1
COMMENTS
Since the even anti-tau numbers (A268066) are square numbers, all the terms are either of the form 4*k^2 - 1 or 4*k^2.
LINKS
EXAMPLE
3 is a term since 3 and 4 are both anti-tau numbers: gcd(3, tau(3)) = gcd(3, 2) = 1 and gcd(4, tau(4)) = gcd(4, 3) = 1.
MATHEMATICA
antiTauQ[n_] := CoprimeQ[n, DivisorSigma[0, n]]; s = {}; Do[k = 4*n^2; If[antiTauQ[k], If[antiTauQ[k - 1], AppendTo[s, k - 1]]; If[antiTauQ[k + 1], AppendTo[s, k]]], {n, 1, 50}]; s
CROSSREFS
Subsequence of A046642 and A081350.
Sequence in context: A083061 A363561 A285475 * A136641 A325186 A053359
KEYWORD
nonn
AUTHOR
Amiram Eldar, Feb 19 2021
STATUS
approved

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Last modified May 22 09:32 EDT 2024. Contains 372745 sequences. (Running on oeis4.)