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 A139096 Infraperfect numbers: 2^(2p - 1) - 2^p, where p is A000043(n). 2
 4, 24, 480, 8064, 33546240, 8589803520, 137438429184, 2305843007066210304, 2658455991569831743501771111346995200, 191561942608236107294793377774818628309652252823388160 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS Difference between n-th even perfect number and n-th even superperfect number A061652(n). Difference between n-th ultraperfect number A139306(n) and n-th Mersenne prime A000668(n), minus 1. Also, difference between n-th perfect number A000396(n) and n-th superperfect number A019279(n), if there are no odd perfect and superperfect numbers. LINKS FORMULA a(n) = 2^(2*A000043(n) - 1) - 2^A000043(n) = A139306(n) - 2^A000043(n) = A139306(n) - A000668(n) - 1 = A139306(n) - (A000668(n)+1) = A139306(n) - 2*A061652(n) = A139306(n) - A072868(n). EXAMPLE a(2)=24 because A000043(2)=3 then 2^(2*3 - 1) - 2^3 = 2^5 - 2^3 = 32 - 8 = 24. CROSSREFS Cf. A000396, A000668, A019279, A061652, A072868, A139306. Sequence in context: A103624 A101952 A009535 * A111425 A013100 A013061 Adjacent sequences:  A139093 A139094 A139095 * A139097 A139098 A139099 KEYWORD nonn AUTHOR Omar E. Pol, Apr 22 2008 EXTENSIONS More terms from R. J. Mathar, Feb 05 2010 STATUS approved

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Last modified April 17 19:51 EDT 2021. Contains 343070 sequences. (Running on oeis4.)