A131984 Where records occur in A106708.

1, 4, 6, 8, 10, 12, 18, 20, 24, 30, 36, 48, 60, 84, 90, 120, 168, 180, 240, 336, 360, 420, 480, 540, 600, 660, 720, 840, 1080, 1260, 1440, 1680, 2160, 2520, 3360, 3780, 4200, 4620, 5040, 7560, 9240, 10080, 12600, 13860, 15120, 18480, 20160, 25200, 27720

Offset

1,2

Comments

Numbers n such that concatenation of proper divisors of n exceeds that of all smaller numbers. Empty concatenation is regarded as 0.

Sequence has many terms in common with A034090 (numbers n such that sum of proper divisors of n exceeds that of all smaller numbers), A034287 (numbers n such that product of divisors of n is larger than for any number less than n), A034288 (product of proper divisors is larger than for any smaller number), A067128 (Ramanujan's largely composite numbers, defined to be n such that d(n) >= d(k) for k = 1 to n-1).

Links

Klaus Brockhaus, Table of n, a(n) for n=1..144

Mathematica

DeleteDuplicates[Table[{n, If[CompositeQ[n], FromDigits[Flatten[IntegerDigits/@Rest[ Most[ Divisors[n]]]]], 0]}, {n, 30000}], GreaterEqual[#1[[2]], #2[[2]]]&][[;; , 1]] (* Harvey P. Dale, Apr 27 2024 *)

Prog

(PARI) {map(n) = local(d); d=divisors(n); if(#d<3, 0, d[1]=""; eval(concat(vecextract(d, concat("..", #d-1)))))} {m=28000; r=-1; for(n=1, m, if(r<(a=map(n)), r=a; print1(n, ", ")))}

Crossrefs

Cf. A106708, A131983 (records), A034090, A034287, A034288, A067128.

Sequence in context: A163248 A341280 A034288 * A359330 A307542 A225510

Adjacent sequences: A131981 A131982 A131983 * A131985 A131986 A131987

Keyword

nonn,base,changed

Author

Klaus Brockhaus, Aug 05 2007

Status

approved