A009441 - OEIS

A009441

a(n) is the concatenation of n and 7n.

17, 214, 321, 428, 535, 642, 749, 856, 963, 1070, 1177, 1284, 1391, 1498, 15105, 16112, 17119, 18126, 19133, 20140, 21147, 22154, 23161, 24168, 25175, 26182, 27189, 28196, 29203, 30210, 31217, 32224, 33231, 34238, 35245, 36252, 37259, 38266, 39273, 40280

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OFFSET

1,1

LINKS

Vincenzo Librandi, Table of n, a(n) for n = 1..1000

MATHEMATICA

nxt[n_]:=Module[{idn=IntegerDigits[n], idn7=IntegerDigits[7n]}, FromDigits[Join[idn, idn7]]]; Array[nxt, 100] (* Vincenzo Librandi, Feb 04 2014 *)

Table[n*10^IntegerLength[7n]+7n, {n, 40}] (* Harvey P. Dale, Aug 02 2024 *)

PROG

(Magma) [Seqint(Intseq(7*n) cat Intseq(n)): n in [1..50]]; // Vincenzo Librandi, Feb 04 2014

CROSSREFS

Cf. concatenation of n and k*n: A020338 (k=1), A019550 (k=2), A019551 (k=3), A019552 (k=4), A019553 (k=5), A009440 (k=6), this sequence (k=7), A009470 (k=8), A009474 (k=9).

Sequence in context: A070137 A021054 A016246 * A016293 A139733 A016185

Adjacent sequences: A009438 A009439 A009440 * A009442 A009443 A009444

KEYWORD

nonn,base,less,easy

AUTHOR

David W. Wilson

STATUS

approved