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A078275 a(n) is the number from which if odd-positioned digits are deleted then one gets the concatenation of first n even numbers, while if even-positioned digits are deleted then one gets reverse concatenation of first n even numbers. Position of least significant digit is considered to be 1. 3
22, 2442, 264462, 28466482, 214068861402, 2142618018061422, 21446182110018261442, 214661841102112018461462, 2148618611041122114018661482, 22406188110611241142116018862402, 224262801108112611441162118028062422, 2244628212001128114611641182210028262442 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

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

EXAMPLE

a(4) = 28466482: deleting alternate digits starting from the LSD gives 2468. Deleting the other ones gives 8642.

PROG

(PARI) a(n) = {my(d, v=w=[2]); for(i=2, n, v=concat(v, d=digits(2*i)); w=concat(d, w)); fromdigits(vector(2*#v, i, if(i%2, v[1+i\2], w[i/2]))); } \\ Jinyuan Wang, May 17 2020

CROSSREFS

Cf. A078274, A078276, A078277, A078278.

Sequence in context: A098130 A078278 A231053 * A200805 A128854 A114942

Adjacent sequences:  A078272 A078273 A078274 * A078276 A078277 A078278

KEYWORD

nonn,base

AUTHOR

Amarnath Murthy, Nov 25 2002

EXTENSIONS

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

a(11)-a(12) from Jinyuan Wang, May 17 2020

STATUS

approved

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