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A214963 a(0)=a(1)=1, a(n) = least k>a(n-1) such that k*a(n-2) is an oblong number. 4
1, 1, 2, 6, 10, 12, 21, 35, 36, 70, 112, 117, 230, 368, 390, 759, 763, 1290, 2244, 2292, 3133, 3580, 4170, 5154, 5355, 7014, 7710, 9160, 9328, 11592, 19274, 22616, 27555, 37290, 37312, 40756, 47820, 63680, 68862, 87450, 93730, 108985, 110262, 132888, 137731, 159159 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,3

LINKS

Table of n, a(n) for n=0..45.

MAPLE

isA002378 := proc(n)

    if issqr(1+4*n) then

        (sqrt(1+4*n)-1) /2 ;

        type(%, 'integer') ;

    else

        false;

    end if;

end proc:

A214963 := proc(n)

    option remember;

    local k ;

    if n <= 1 then

        1;

    else

        for k from procname(n-1)+1 do

            if isA002378(k*procname(n-2)) then

                return k;

            end if;

        end do:

    end if;

end proc: # R. J. Mathar, Aug 10 2012

CROSSREFS

Cf. A002378.

Sequence in context: A190789 A071638 A028348 * A140776 A277238 A108783

Adjacent sequences:  A214960 A214961 A214962 * A214964 A214965 A214966

KEYWORD

nonn

AUTHOR

Alex Ratushnyak, Aug 03 2012

STATUS

approved

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Last modified June 16 12:38 EDT 2019. Contains 324152 sequences. (Running on oeis4.)