A308938 - OEIS

A308938

Smallest deficient number which is the product of n consecutive primes.

1, 2, 15, 105, 1155, 85085, 1616615, 37182145, 1078282205, 247357937827, 10141675450907, 436092044389001, 20496326086283047, 1086305282573001491, 64092011671807087969, 3909612711980232366109, 261944051702675568529303, 18598027670889965365580513

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OFFSET

0,2

COMMENTS

a(n) is greater than A087234(n) for n = 2, 5, 6, 9, 10, 11, 12, 13, 14, 18, ... By definition, A087234(n) is never greater than a(n).

LINKS

Table of n, a(n) for n=0..17.

EXAMPLE

a(5) = 5*7*11*13*17 = 85085.

MATHEMATICA

a[n_] := Module[{p = Prime@Range[n]}, While[Times@@(1+1/p) >= 2, p = Rest @ AppendTo[p, NextPrime@p[[-1]]]]; Times@@p]; Array[a, 18, 0] (* Amiram Eldar, Jul 04 2019 *)

PROG

(PARI) a(n)=for(k=1, +oo, p=prod(i=k, k+n-1, prime(i)); sigma(p)<2*p && return(p))

CROSSREFS

Cf. A087234, A073485, A005100.

Sequence in context: A295268 A037524 A037733 * A037556 A037492 A037572

Adjacent sequences: A308935 A308936 A308937 * A308939 A308940 A308941

KEYWORD

nonn,easy

AUTHOR

Jeppe Stig Nielsen, Jul 01 2019

STATUS

approved