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 A321687 a(n) = (2*n+1)-digit palindrome formed by first concatenating A158289(i) for i=1..n+1 and then A158289(n-j) for j=1..n. 0
 1, 121, 12321, 1234321, 123454321, 12345654321, 1234567654321, 123456787654321, 12345678987654321, 1234567898987654321, 123456789878987654321, 12345678987678987654321, 1234567898765678987654321, 123456789876545678987654321, 12345678987654345678987654321 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,2 LINKS EXAMPLE 1                     121                    12321                   1234321                  123454321                 12345654321                1234567654321               123456787654321              12345678987654321             1234567898987654321            123456789878987654321           12345678987678987654321          1234567898765678987654321         123456789876545678987654321        12345678987654345678987654321       1234567898765432345678987654321      123456789876543212345678987654321     12345678987654321012345678987654321    1234567898765432101012345678987654321   123456789876543210121012345678987654321 PROG (PARI) a158289(n)=abs(n-round(n/18)*18) eva(n) = subst(Pol(n), x, 10) a(n) = if(n==0, return(1)); my(v=vector(2*n+1), x=#v); for(k=1, ceil(#v/2), v[k]=a158289(k)); while(1, v[x]=v[#v-x+1]; x--; if(x==ceil(#v/2), return(eva(v)))) CROSSREFS Cf. A158289. Sequence in context: A137466 A062689 A057139 * A002477 A173426 A261570 Adjacent sequences:  A321684 A321685 A321686 * A321688 A321689 A321690 KEYWORD nonn,base,easy AUTHOR Felix FrÃ¶hlich, Nov 17 2018 STATUS approved

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Last modified December 12 15:11 EST 2019. Contains 329960 sequences. (Running on oeis4.)