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A078274 a(n) is the number from which if odd-positioned digits are deleted then one gets the concatenation of first n odd numbers, while if even-positioned digits are deleted then one gets reverse concatenation of first n odd numbers. Position of least significant digit is considered to be 1. 3
11, 1331, 153351, 17355371, 1937557391, 11315977951311, 133151719917151331, 1531537191111917351351, 17315571931111113917551371, 193157719511131131115917751391, 1132597197111511331151117917952311, 13325172991117113511531171119927152331 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Table of n, a(n) for n=1..12.

EXAMPLE

a(4) = 17355371: deleting alternate digits starting from the LSD gives 1357. Deleting the other digits gives 7531.

MATHEMATICA

rif[n_]:=Module[{idn=Flatten[IntegerDigits/@Range[1, 2n-1, 2]]}, FromDigits[ Riffle[idn, Reverse[idn]]]]; Array[rif, 15] (* Harvey P. Dale, Apr 11 2012 *)

CROSSREFS

Cf. A078275, A078276, A078277, A078278.

Sequence in context: A182553 A223039 A209093 * A013716 A110195 A015484

Adjacent sequences:  A078271 A078272 A078273 * A078275 A078276 A078277

KEYWORD

base,nonn

AUTHOR

Amarnath Murthy, Nov 25 2002

EXTENSIONS

More terms from Antonio G. Astudillo (afg_astudillo(AT)lycos.com), Apr 19 2003

Corrected and extended by Harvey P. Dale, Apr 11 2012

STATUS

approved

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Last modified July 12 04:30 EDT 2020. Contains 335658 sequences. (Running on oeis4.)