The OEIS is supported by the many generous donors to the OEIS Foundation. Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A258270 Consider the unitary aliquot parts, in ascending order, of a composite number. Take their sum and repeat the process deleting the minimum number and adding the previous sum. The sequence lists the numbers that after some iterations reach a sum equal to the reverse of themselves. 1
 6, 75, 133, 1005, 1603, 4258, 5299, 84292, 89944, 170568, 192901, 303003, 695364, 1633303 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 LINKS Eric Weisstein's World of Mathematics, Unitary Divisor Eric Weisstein's World of Mathematics, Unitary Divisor Function Eric Weisstein's World of Mathematics, Unitary Perfect Number Wikipedia, Unitary divisor EXAMPLE Divisors of 6 are 1, 2, 3, 6. Unitary aliquot parts are 1, 2, 3. We have: 1 + 2 + 3 = 6 that is equal to its reverse; Divisors of 75 are 1, 3, 5, 15, 25, 75. Unitary aliquot parts are 1, 3, 25. We have: 1 + 3 + 25 = 29; 3 + 25 + 29 = 57 that is the reverse of 75; Divisors of 84292 are 1, 2, 4, 13, 26, 52, 1621, 3242, 6484, 21073, 42146, 84292. Unitary aliquot parts are 1, 4, 13, 52, 1621, 6484, 21073. We have: 1 + 4 + 13 + 52 + 1621 + 6484 + 21073 = 29248 that is the reverse of 84292; MAPLE with(numtheory): R:=proc(w) local x, y; x:=w; y:=0; while x>0 do y:=10*y+(x mod 10); x:=trunc(x/10); od: y; end: P:=proc(q, h) local a, b, c, k, n, t, v; v:=array(1..h); for n from 1 to q do if not isprime(n) then a:=sort([op(divisors(n))]); b:=[]; c:=ilog10(n)+1; for k from 1 to nops(a)-1 do if gcd(a[k], n/a[k])=1 then b:=[op(b), a[k]]; fi; od; if nops(b)>1 then for k from 1 to nops(b) do v[k]:=b[k]; od; t:=nops(b)+1; v[t]:=add(v[k], k=1..nops(b)); if R(v[t])=n then print(n); else while ilog10(v[t])+1<=c do t:=t+1; v[t]:=add(v[k], k=t-nops(b)..t-1); if R(v[t])=n then print(n); break; fi; od; fi; fi; fi; od; end: P(10^9, 1000); CROSSREFS Cf. A246544, A247012, A258142. Sequence in context: A269334 A069852 A266574 * A281797 A049235 A129031 Adjacent sequences:  A258267 A258268 A258269 * A258271 A258272 A258273 KEYWORD nonn,more,base AUTHOR Paolo P. Lava, May 25 2015 STATUS approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recents
The OEIS Community | Maintained by The OEIS Foundation Inc.

Last modified May 24 19:38 EDT 2022. Contains 354043 sequences. (Running on oeis4.)