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 A179651 Difference between consecutive practical numbers. 0
 1, 2, 2, 2, 4, 4, 2, 2, 4, 4, 2, 2, 4, 4, 2, 6, 6, 2, 4, 4, 2, 6, 6, 2, 4, 4, 2, 6, 4, 4, 4, 4, 8, 6, 2, 4, 8, 4, 6, 6, 4, 2, 6, 8, 4, 12, 4, 2, 2, 4, 4, 2, 6, 4, 4, 4, 6, 6, 12, 4, 4, 4, 6, 2, 4, 4, 8, 6, 6, 4, 2, 2, 4, 8, 4, 6, 6, 4, 2, 6, 4, 8, 4, 4, 10, 2, 4, 6, 2, 4, 4, 8, 6, 2, 4, 12, 8, 8, 2, 6, 4, 2, 2 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS First occurrence of 2k, k=1..: 2, 5, 16, 33, 85, 46, 331, 188, 171, 300, 1986, 962, 3321, 968, 2316, 6514, 9974, 3219, ..., . - Robert G. Wilson v, Jul 23 2010 LINKS EXAMPLE For n=3, this is 6-4=2. For n=5, this is 12-8=4. MATHEMATICA PracticalQ[n_] := Module[{f, p, e, prod = 1, ok = True}, If[n < 1 || (n > 1 && OddQ[n]), False, If[n == 1, True, f = FactorInteger[n]; {p, e} = Transpose[f]; Do[ If[ p[[i]] > 1 + DivisorSigma[1, prod], ok = False; Break[]]; prod = prod*p[[i]]^e[[i]], {i, Length[p]}]; ok]]]; s = Select[ Range@ 479, PracticalQ]; Rest@s - Most@s (* Robert G. Wilson v, Jul 23 2010 *) CROSSREFS Cf. A005153. Sequence in context: A071472 A064135 A332476 * A139560 A192095 A105080 Adjacent sequences:  A179648 A179649 A179650 * A179652 A179653 A179654 KEYWORD easy,nonn AUTHOR Jason G. Wurtzel, Jul 22 2010 EXTENSIONS a(20) onwards from Robert G. Wilson v, Jul 23 2010 STATUS approved

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Last modified June 24 05:58 EDT 2021. Contains 345416 sequences. (Running on oeis4.)