1,2

Also called Smarandache symmetric numbers.

M. Le, The Primes in the Smarandache Symmetric Sequences, Smarandache Notions Journal, Vol. 10, No. 1-2-3, 1999, 174-175.

F. Smarandache, "Only Problems, not Solutions!", Xiquan Publ., Phoenix-Chicago, 1993

M. L. Perez et al., eds., Smarandache Notions Journal

Eric Weisstein's World of Mathematics, Link to a section of The World of Mathematics.

F. Smarandache, Only Problems, Not Solutions!

a(n)=a1+a2+a3, where a1=floor{a(n-1)/[10^(k+y*w)]}*10^(k+w+y*k2) a2=(w2*y2+b*y)*10^(k+y*w) a3=a(n-1)-floor{a(n-1)/[10^(k+y*w)]}*10^(k+y*w) being k=floor{(floor[1+log10(a(n-1)))-x*w]/2} k2=floor[1+log10(b)] x=[3+(-1)^(n+1)]/2 y=[1+(-1)^(n+1)]/2 y2=[1+(-1)^n]/2 b=[2*n+1+(-1)^(n+1)]/4 w=floor{1+log10[(2*(n-1)+1+(-1)^n)/4]} w2=[2*(n-1)+1+(-1)^n]/4 - Paolo P. Lava (ppl(AT)spl.at), Jun 04 2008

P:=proc(n) local a, a1, a2, a3, b, k, k2, i, w, w2, x, y, y2; a:=1; print(a); for i from 2 by 1 to n do x:=(3+(-1)^(i+1))/2; y:=(1+(-1)^(i+1))/2; y2:=(1+(-1)^i)/2; b:=(2*i+1+(-1)^(i+1))/4; w:=floor(evalf(1+log10((2*(i-1)+1+(-1)^i)/4), 1000)); w2:=(2*(i-1)+1+(-1)^i)/4; k:=floor((floor(evalf(1+log10(a), 1000))-(x)*w)/2); k2:=floor(evalf(1+log10(b), 1000)); a1:=floor(evalf(a/(10^(k+y*w)), 1000))*10^(k+w+y*k2); a2:=(w2*y2+b*y)*10^(k+y*w); a3:=a-floor(evalf(a/10^(k+y*w), 1000))*10^(k+y*w); a:=a1+a2+a3; print(a); od; end: P(500); - Paolo P. Lava (ppl(AT)spl.at), Jun 04 2008

Sequence in context: A106473 A125315 A132583 this_sequence A088113 A045587 A059734

Adjacent sequences: A007904 A007905 A007906 this_sequence A007908 A007909 A007910

nonn,base

R. Muller