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 A195613 Numbers n with property that n, 2n-1 and 2n+1 are composite. 0
 25, 28, 32, 38, 46, 58, 60, 62, 72, 77, 80, 85, 88, 92, 93, 94, 102, 104, 108, 110, 118, 122, 123, 124, 130, 133, 143, 144, 145, 148, 150, 152, 160, 161, 162, 164, 170, 171, 172, 178, 182, 185, 188, 196, 202, 203, 206, 207, 208, 212, 213, 214, 218, 226, 235 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS In A000027, if n, n+(n-1) and n+(n+1) are composite, then n is a term of this sequence. Suggestion: there are arbitrarily long sets of consecutive integers, e.g., 632..637, 665..672, 6428..6443. LINKS MATHEMATICA Select[Range[2, 1000], !PrimeQ[2#-1]&&!PrimeQ[#]&&!PrimeQ[2#+1]&] Select[Range[250], AllTrue[{#, 2#-1, 2#+1}, CompositeQ]&] (* Harvey P. Dale, Feb 26 2022 *) CROSSREFS Sequence in context: A345509 A295748 A254226 * A127652 A303812 A334534 Adjacent sequences:  A195610 A195611 A195612 * A195614 A195615 A195616 KEYWORD nonn AUTHOR Zak Seidov, Sep 21 2011 STATUS approved

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Last modified August 14 10:20 EDT 2022. Contains 356114 sequences. (Running on oeis4.)