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 A206770 Smallest number k such that sigma(k-2*n)=sigma(k)-2*n. 1
 5, 7, 11, 11, 13, 17, 17, 19, 23, 23, 29, 29, 21, 31, 37, 37, 37, 41, 28, 33, 47, 47, 53, 53, 53, 59, 59, 44, 61, 67, 67, 67, 71, 57, 73, 79, 79, 79, 83, 83, 69, 89, 74, 101, 68, 97, 97, 85, 101, 103, 107, 107, 109, 113, 93, 131, 127, 127, 131, 127, 127, 127 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS Note all k>=1 are considered, even if k-2n<0. If the search space is k>=2n, variants of A020484 and A060264 appear. - R. J. Mathar, Jan 12 2013 LINKS EXAMPLE a(15)=37 because 37 is the minimum number for which sigma(37-2*15)=sigma(7)=8 and sigma(37)-2*15=38-30=8. MAPLE A206770:=proc(q) local k, n; for n from 1 to q do for k from 1 to q do   if sigma(k-2*n)=sigma(k)-2*n then print(k); break; fi; od; od; end: A206770(1000000000); A206770 := proc(n)     local k ;     for k from 1 do         if numtheory[sigma](k-2*n) = numtheory[sigma](k)-2*n then             return k;         end if;     end do: end proc: # R. J. Mathar, Jan 12 2013 CROSSREFS Cf. A054906 Sequence in context: A104200 A249916 A115044 * A107257 A275515 A098806 Adjacent sequences:  A206767 A206768 A206769 * A206771 A206772 A206773 KEYWORD nonn AUTHOR Paolo P. Lava, Jan 10 2013 STATUS approved

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Last modified October 23 12:50 EDT 2019. Contains 328345 sequences. (Running on oeis4.)