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.

22, 2442, 264462, 28466482, 214068861402, 2142618018061422, 21446182110018261442, 214661841102112018461462, 2148618611041122114018661482, 22406188110611241142116018862402, 224262801108112611441162118028062422, 2244628212001128114611641182210028262442

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