a^2+na=221
,
{a^2 +2[[(a-1)/2]2-1]-[(a-2)2+2[[(a-2-1)/2]^2-1]]-34}/6=k
,
{(k+1)^2 +2[[((k+1)-1)/2]2-1]-[((k+1)-2)2+2*[[((k+1)-2-1)/2]^2-1]]-34}/6=0
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From @logicalworld
a^2+na=221
,
{a^2 +2[[(a-1)/2]2-1]-[(a-2)2+2[[(a-2-1)/2]^2-1]]-34}/6=k
,
{(k+1)^2 +2[[((k+1)-1)/2]2-1]-[((k+1)-2)2+2*[[((k+1)-2-1)/2]^2-1]]-34}/6=0