A066266
Product of first n primorials + 1.
Original entry on oeis.org
3, 13, 361, 75601, 174636001, 5244319080001, 2677277333530800001, 25968760179275365452000001, 5793445238736255798985527240000001, 37481813439427687898244906452608585200000001, 7517370874372838151564668004911177464757864076000000001
Offset: 1
a(3)=361 since 361 = (2)*(2*3)*(2*3*5) + 1.
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Table[Times@@Table[Times@@Prime[Range[n]],{n,k}]+1,{k,40}] (* Jayanta Basu, May 12 2013 *)
Rest[FoldList[Times,1,Rest[FoldList[Times,1,Prime[Range[10]]]]]]+1 (* Harvey P. Dale, Sep 16 2013 *)
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a(n) = 1 + prod(k=1, n, prime(k)^(n-k+1)) \\ Andrew Howroyd, Dec 10 2024
A066268
Product of first n primorials - 1.
Original entry on oeis.org
1, 11, 359, 75599, 174635999, 5244319079999, 2677277333530799999, 25968760179275365451999999, 5793445238736255798985527239999999, 37481813439427687898244906452608585199999999, 7517370874372838151564668004911177464757864075999999999
Offset: 1
a(3) = (2)*(2*3)*(2*3*5) - 1 = 359.
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Table[Times@@Table[Times@@Prime[Range[n]],{n,k}]-1,{k,40}]
(* or *)
pr2=1; Table[pr1=1; Do[pr1=pr1*Prime[n],{n,k}]; pr2=pr2*pr1; pr2-1,{k,40}] (* Jayanta Basu, May 12 2013 *)
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a(n) = -1 + prod(k=1, n, prime(k)^(n-k+1)) \\ Andrew Howroyd, Dec 10 2024
A088844
Multiply perfect numbers k for which the quotient sigma_3(k)/k = A001158(k)/k is nonintegral.
Original entry on oeis.org
28, 2178540, 45532800, 142990848, 14182439040, 43861478400, 518666803200, 704575228896, 13661860101120, 181742883469056, 740344994887680, 20158185857531904, 275502900594021408, 71065075104190073088, 87934476737668055040, 154345556085770649600, 1161492388333469337600
Offset: 1
A066267
Numbers k such that A066266(k) is prime.
Original entry on oeis.org
1, 2, 5, 12, 15, 35
Offset: 1
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t={}; Do[If[PrimeQ[Times@@Table[Times@@Prime[Range[n]],{n,k}]+1],AppendTo[t,k]],{k,35}]; t (* Jayanta Basu, May 12 2013 *)
A088845
Multiply perfect numbers k for which the quotient sigma_5(k)/k = A001160(k)/k is nonintegral.
Original entry on oeis.org
496, 523776, 23569920, 142990848, 275502900594021408, 622286506811515392, 71065075104190073088, 34384125938411324962897920, 41254809330254618094796800000, 2360137508360958913826987704320, 11990459635691909131039408128000, 24862223033124742964111030747136
Offset: 1
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lista() = {v = readvec("b007691.txt"); for (i=1, #v, vi = v[i]; if (sigma(vi, 5) % vi, print1(vi, ", ");););} \\ Michel Marcus, Dec 26 2013
A088846
Multiply perfect numbers k for which the quotient sigma_7(k)/k = A013955(k)/k is nonintegral.
Original entry on oeis.org
8128, 1476304896, 66433720320, 403031236608, 14942123276641920, 170206605192656148480, 1802582780370364661760, 1940351499647188992000, 4010059765937523916800, 352338107624535891640320, 156036748944739017459105792, 2827987212986831882236723200, 15229814702070563916152832000
Offset: 1
Showing 1-6 of 6 results.
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