A078568 Repunits concatenated with A000422, where A000422 is the concatenation of numbers from n down to 1.

11, 1121, 111321, 11114321, 1111154321, 111111654321, 11111117654321, 1111111187654321, 111111111987654321, 111111111110987654321, 111111111111110987654321, 111111111111121110987654321

Offset

1,1

Comments

See A078569 for the primes arising in this sequence.

Links

Harvey P. Dale, Table of n, a(n) for n = 1..277

Mathematica

a[n_Integer] := Block[{repUn = Array[Array[1 &, #] &, {n}], nTo1 = Range[ Range@n, 1, -1]}, ToExpression/@ StringJoin/@ Map[ToString, Flatten/@ Thread@{repUn, nTo1}, {2}]]; a[100] (* or *)
a[n_Integer] := FromDigits /@ StringJoin /@ Table[ Join[ PadLeft[{}, i, "1"], ToString /@ Range[i, 1, -1]], {i, n}]; a[100] (* Mikk Heidemaa, May 03 2021 *)
Table[FromDigits[Join[PadRight[{}, n, 1], Flatten[IntegerDigits/@Range[n, 1, -1]]]], {n, 20}] (* Harvey P. Dale, Aug 23 2022 *)

Crossrefs

Cf. A002275, A000422, A078569.

Sequence in context: A343837 A303067 A075600 * A015095 A167118 A045981

Adjacent sequences: A078565 A078566 A078567 * A078569 A078570 A078571

Keyword

base,nonn

Author

Jason Earls, Nov 29 2002

Status

approved