proposed

approved

editing

proposed

a(n) = 100^[n/10] + 2*n*10^[n/10]: inspired by Engel expansion of Pi.

G. C. Greubel, <a href="/A137507/b137507.txt">Table of n, a(n) for n = 0..1000</a>

Table[100^(Floor[n/10]) + 2*n*10^(Floor[n/10]), {n, 0, 50}] (* G. C. Greubel, Feb 23 2017 *)

(PARI) a(n) = (n+5 + 10^(floor((n+5)/10)))^2 - (n+5)^2; for (n=1, 30, print1(" "a(n)" ")) \\ changed n+5 to n. - _M. F. Hasler, _, May 02 2008

(PARI) vector(30, n, n--; 2*n*10^(n\10) + 100^(n\10)) \\ - _M. F. Hasler, _, May 02 2008

approved

editing

Edited by _M. F. Hasler (www.univ-ag.fr/~mhasler) _ and N. J. A. Sloane, May 02 2008

_Alexander R. Povolotsky (pevnev(AT)juno.com), _, Apr 23 2008

Edited by M. F. Hasler (www.univ-ag.fr/~mhasler) and _N. J. A. Sloane (njas(AT)research.att.com), _, May 02 2008

nonn,new

nonn

Edited by M. F. Hasler (www.univ-ag.fr/~mhasler) and N. J. A. Sloane (njas, (AT)research.att.com), May 02 2008

100^[n/10] + 2*n*10^[n/10]: inspired by Engel expansion of Pi.

1, 3, 5, 7, 9, 11, 13, 15, 17, 19, 300, 320, 340, 360, 380, 400, 420, 440, 460, 480, 14000, 14200, 14400, 14600, 14800, 15000, 15200, 15400, 15600, 15800, 1060000, 1062000, 1064000, 1066000, 1068000, 1070000

0,2

(PARI) a(n) = (n+5 + 10^(floor((n+5)/10)))^2 - (n+5)^2; for (n=1, 30, print1(" "a(n)" ")) \\ changed n+5 to n. - M. F. Hasler, May 02 2008

(PARI) vector(30, n, n--; 2*n*10^(n\10) + 100^(n\10)) \\ - M. F. Hasler, May 02 2008

Cf. A006784.

nonn

Alexander R. Povolotsky (pevnev(AT)juno.com), Apr 23 2008

Edited by M. F. Hasler (www.univ-ag.fr/~mhasler) and njas, May 02 2008

approved