A134733 Concatenation of next n imperfect numbers.

1, 23, 457, 891011, 1213141516, 171819202122, 23242526272930, 3132333435363738, 394041424344454647, 48495051525354555657, 5859606162636465666768, 697071727374757677787980

Offset

1,2

Links

Harvey P. Dale, Table of n, a(n) for n = 1..200

Mathematica

Module[{nn=120, in, len}, in=Select[Range[nn], DivisorSigma[1, #]!=2#&]; len= Floor[x/.Last[Solve[(x(x+1))/2==Length[in]]]]; FromDigits[Flatten[ IntegerDigits/@ #]]&/@TakeList[in, Range[len]]] (* Requires Mathematica version 10 or later *) (* Harvey P. Dale, Mar 01 2020 *)

Crossrefs

Cf. A053067, A132943, A133013. Imperfect numbers: A132999.

Sequence in context: A080479 A053067 A036906 * A328348 A095256 A273008

Adjacent sequences: A134730 A134731 A134732 * A134734 A134735 A134736

Keyword

base,easy,nonn

Author

Omar E. Pol, Nov 12 2007

Status

approved