A283801 Concatenation of the first n odd composite numbers (A071904).

9, 915, 91521, 9152125, 915212527, 91521252733, 9152125273335, 915212527333539, 91521252733353945, 9152125273335394549, 915212527333539454951, 91521252733353945495155, 9152125273335394549515557, 915212527333539454951555763, 91521252733353945495155576365

Offset

1,1

Comments

There are 3 primes in the first 5028 terms of this sequence, see A283802.

Links

Table of n, a(n) for n=1..15.

Eric Weisstein's World of Mathematics, Consecutive Number Sequences

Mathematica

bb[1]=9; bb[n_]:=bb[n]=Which[PrimeQ[bb[n-1]+2]==False, bb[n-1]+2, PrimeQ[bb[n-1]+4]==False, bb[n-1]+4, True, bb[n-1]+6]; coc[n_]:=FromDigits[Flatten[IntegerDigits[Table[bb[k], {k, 1, n}]]]]; Table[coc[n], 14]
f[n_] := Block[{oc = cc = 0, k = 2}, While[oc <= n, If[ OddQ@ k && !PrimeQ@ k, cc = cc*10^IntegerLength[k] +k; oc++]; k++]; cc]; Array[f, 14] (* Robert G. Wilson v, Mar 17 2017 *)

Crossrefs

Cf. A071904, A089933, A132932.

Sequence in context: A332189 A045793 A069054 * A015107 A024124 A316535

Adjacent sequences: A283798 A283799 A283800 * A283802 A283803 A283804

Keyword

base,nonn,easy

Author

XU Pingya, Mar 17 2017

Status

approved